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At least 37 records · Page 2Linked to original sources
PubMed1998

Factors affecting the lifespan of the human dentition in Britain prior to the seventeenth century.

OBJECTIVE: To confirm that compensatory eruption (supereruption) of teeth past a stable periodontium occurs in response to severe occlusal attrition. DESIGN: Regression analysis study from radiographs and direct measurements. SETTING: Archaeological material at the University of Aberdeen. SUBJECTS: 47 individuals > 21 years old and dating from Late Mediaeval times (1300-1600 AD). MAIN OUTCOME MEASURES: Occlusal attrition was recorded on the first permanent mandibular molars. Measurements on radiographs of the teeth from the fixed point of the inferior dental canal were taken to the occlusal surface, the alveolar crest and the tooth apex. Regression analysis was undertaken between these variables and related to attrition (age). RESULTS: Continuous eruption of the permanent human dentition past a stable periodontium does occur in response to tooth height lost by wear, despite the fact that supereruption may lead to the eventual self destruction of the dentition. This mechanism was primarily responsible for the early loss (at 40-45 years of age) of dentitions in Mediaeval times. CONCLUSIONS: Stability of occlusal height appears to be an important function of the dentition and if triggered by severe wear will lead to increasing root exposure and eventual exfoliation of the teeth. It is important not to confuse bone loss due to periodontitis with root exposure due to supereruption of the teeth.

Adult↗
PubMed1983

Effective exposure level and diagnostic performance in endodontic radiography.

Image quality is limited by the information capacity of the image-forming system and can be computed from three parameters: contrast, resolution, and noise. These parameters can be combined to yield a single measure which determines the maximum amount of information obtainable from any x-ray system and is called the noise-equivalent number of quanta (NEQ) per unit area. The effects of image quality, expressed as noise-equivalent number of quanta (NEQ) per unit area, on the radiographic performance by dentists reading the position of an endodontic file in a root canal were studied. Three different speed films were used in conjunction with a fixed screen. NEQ values ranged between 0.64 x 10(4) and 14.3 x 10(4) per square millimeter. Components of variance associated with the position of the tooth apex and the tip of an endodontic file in a root canal were compared for the effect of different NEQs and observers. Results show that the standard deviation in locating a file tip and tooth apex may be a linear function of log NEQ. The estimated standard deviation associated with changes in NEQ was found to be relatively small compared to that observed among dentists. These findings indicate that a significant reduction in exposure would have a relatively small effect on the precision of endodontic distance measurements.

Dental Pulp Cavity↗
PubMed2003

[Clinical studies on apexification with demineralized dentin matrix].

OBJECTIVE: To study the clinical effects of demineralized dentin matrix (DDM) as a apexificating agent. METHODS: Human teeth were crushed into fragments and were deflated, demineralized, lyophilized to produce DDM. The DDM was used as an apexificating agent to treat 57 teeth compared with calcium hydroxide. X-ray film and clinical observation were undertaken after half a year, one year and two years. RESULTS: One year later, a barrier in the tooth apex was found in the X-rays film. Then permanent filling material was used. After two years, DDM group had a healing rate of 92.86%, was higher than that of 91.30% in calcium hydroxide group, but there were no statistical significance. CONCLUSION: The findings suggest that DDM can be used as a new apexificating agent. One year after the apexification is the best opportunity to change the apexificating agent to a permanent root canal filling material.

Adolescent↗
PubMed1992

[Skin symptoms of chronic inflammation of a tooth root apex].

Cutaneous manifestations of a periradicular inflammation are now uncommon. In most cases the periradicular infection results in the development of an apical granuloma. If there is proliferation of resting epithelial cells in this granuloma a cyst will develop, the so-called radicular cyst. A rare form of periradicular inflammation is the so-called chronisch granulierende Entzündung nach Partsch [Partsch's chronic granulomatous inflammation]. In this case the granulation tissue spreads through the bone and results in a cutaneous odontogenic sinus. We report on a female patient in whom complete healing was obtained by removal of the periradicular process and excision of the sinus tract.

Adult↗
PubMed1989

[Analysis of movement in partial prostheses and abutment teeth with differences in retainer].

When designing a prosthesis in a clinical setting that takes into consideration the protection of the abutment teeth and alveolar ridge, it remains difficult to carry out a method of connecting the abutment tooth and prosthesis based on objective grounds. This is because there are still many matters that remain unclear about dynamics of the stomatognathic system, including the prosthesis, when attached in the oral cavity. The author created the following three prostheses on a stimulation model of a tooth bone saddle that included an artificial mucous membrane and periodontal membrane: (1) A fixed bridge, (2) A telescopic denture (Konuskronen Telescope), (3) An Akers clasp denture. Following this, flat-controlled random noise was applied to each denture to create a dynamic load that exhibits a state closer to a clinical situation. Modal analysis was carried out with a laser doppler vibrometer and observations were made of the prosthesis and the abutment tooth apex to obtain visual clarification of dynamics, The following results were obtained. 1. As far modal resonant frequency, in mode #1, the bridge measured at 483 Hz and 561 Hz, the Telescope at 452 Hz and 600 Hz and the clasp at 581 Hz and 596 Hz. In mode #2 the bridge measured at 1,355 Hz and 1,370 Hz, the Telescope at 1,343 and 1,040 Hz and the clasp at 1,114 Hz and 1,079 Hz. In mode #3, only the bridge was detected and the recorded values 1,906 Hz and 2,026 Hz. 2. The influence on the modal resonant frequency due to the difference in abutment devices was limited. 3. Observation of animation indicated that the tendency for lateral movement of the abutment teeth increased going from the bridge to the Telescope to the clasp. 4. Displacement of the abutment tooth root apex decreased in reverse proportion to the strength of the connection between the abutment tooth and the abutment device.

Dental Abutments↗
PubMed1991

A new endodontic stabilizer implant device.

A new endodontic stabilizer implant device is presented that can be used immediately after enucleation of large periapical cysts. The force transmission characteristics of this implant were evaluated by means of photoelasticity. The implant served to distribute incisal forces within the supporting structure. Improved stress conditions resulted at the tooth apex and between the apex and the superior border of the implant when the tooth was subjected to apicoectomy.

Apicoectomy↗
PubMed1986

Tooth pulp-evoked jaw-opening reflex in the cat: evidence for central facilitation induced by noxious discharge in the intradental nerve fibers.

The tooth pulp-evoked jaw-opening reflex was studied in the barbiturate-anesthetized cat. At liminal intensity of the stimulus, a stable short-latency response was obtained in the digastricus and in the tongue. At a higher stimulus intensity, there occasionally appeared to be a prolonged discharge of variable duration in the digastricus, and a second period of activity in the tongue after a silent period. The threshold intensity for these late discharges was supraliminal for the intradental A-fibers and subliminal for intradental C-fibers. Noxious conditioning stimulation of a tooth led to a temporary decrease of the threshold for the jaw-opening reflex elicited from a contralateral or adjacent tooth; only conditioning stimulation at an intensity producing a marked arousal reaction was effective in this respect. Infiltration of the tooth apex with epinephrine produced a local elevation of the threshold for the tooth pulp-evoked jaw-opening reflex. Distant noxious conditioning stimulation (tail pinch) did not influence the jaw-opening threshold. The results indicated that based on some central mechanisms, conditioning noxious stimulation of a tooth can produce a facilitation of the jaw-opening reflex.

Animals↗
PubMed1994

A comparative physiological and morphological study of periodontal ligament mechanoreceptors represented in the trigeminal ganglion and the mesencephalic nucleus of the cat.

A correlative morphological study was carried out on two electrophysiologically identified and located periodontal ligament mechanoreceptors in anaesthetised cats. One mechanoreceptor had its cell body in the mesencephalic nucleus and the other had its cell body in the trigeminal ganglion. Physiological recordings were made from each of their cell bodies. The two receptors were located by punctate and electrical stimuli in the labial aspect of the periodontal ligament of the left mandibular canine tooth. Both receptors had similar positions relative to the tooth apex and fulcrum and were situated in the labial part of the ligament in each tooth. The receptor loci were marked, and these regions were studied in a series of semi-thin and ultra-thin sections. Only Ruffini nerve endings were observed under each ink mark. Both Ruffini nerve endings branched, were unencapsulated and were incompletely surrounded by terminal Schwann cells with extensions projecting towards collagen bundles. The results indicate that periodontal ligament mechanoreceptors with cell bodies in the mesencephalic nucleus and those with their cell bodies in the trigeminal ganglion can both be Ruffini nerve endings. Furthermore, there was no apparent morphological difference between the two periodontal ligament mechanoreceptors.

Animals↗
PubMed2001

The "Tip-Edge" torquing mechanism: a mathematical validation.

The Tip-Edge (TP Orthodontics, LaPorte, Ind) bracket is unique among orthodontic brackets because it can be used in combination with rectangular archwire to torque teeth, not through activation of the archwire itself but through the action of auxiliary springs that are active in the tip plane. The purpose of this report is to describe the way in which a tipping couple generates a secondary torquing couple and the resulting path traced by the root apex and to express those actions mathematically. The magnitude of forces applied by the auxiliary spring to the tooth apex is calculated on the basis of an experiment.

Adolescent↗
PubMed1996

Hard tissue of teeth and their calcium and phosphate content in Ambystoma mexicanum (Urodela: Ambystomatidae).

The wall of the pulp cavity, fracture faces and the demineralized surfaces of teeth from larvae and adults of Ambystoma mexicanum were investigated by scanning electron microscopy (SEM). Calcium and phosphate contents were determined by microanalysis. The apical part of the tooth (crown, tooth apex) contains dentin canals. In the larva, these do not reach the enamel-dentin border but end below this border in front of a denser hard substance, possibly enameloid. The pedicel in the adult and the basal portion of the tooth in the larva (base) are without dentin canals. These parts of the teeth are characterized by longitudinally arranged collagen fibres as visualized on the demineralized surfaces. These observations indicate a congruency in early-larval and adult teeth between base and pedicel as well as apex and crown. This partition is also confirmed by the calcium and phosphate values which were identical in larvae and adults. Highest values are found in enamel and lowest values in the tooth-bearing bone. Calcium and phosphate content show a clear difference between dentin and the basal part of the tooth (pedicel and base). The ring-like dividing zone in the adult tooth is less well mineralized.

Ambystoma mexicanum↗
PubMed1987

Intra-vascular thrombosis associated with dental ultrasound.

Ultrasonic instruments used in dentistry generally operate at frequencies of 25 to 42 kHz. A wire oscillating at these ultrasonic frequencies immersed in a liquid produces local flow patterns termed acoustic microstreaming. Large shear forces are produced which are able to rupture erythrocytes and platelets both in vitro and in vivo. This results in activation of the blood coagulation system with subsequent thrombus formation. The probe tip of an ultrasonic scaler was positioned to touch a mammalian mesenteric artery. The probe was operated for 10 to 20 s at a displacement amplitude of 15 micron. Acoustic microstreaming occurred which disturbed blood flow and this microstreaming ceased when the power was switched off. After continued operation of the probe, thrombi were formed against the vessel wall with fragments embolising downstream. These thrombi eventually grew to occlude the vessel. Furthermore, an in situ model demonstrated that acoustic energy was transmitted through the tooth during typical ultrasonic scaling procedures. As a consequence of these observations, it is possible that acoustic microstreaming fields may be generated within the blood vessels entering the tooth apex which are large enough to induce platelet damage. Therefore there is a potential hazard from the use of the ultrasonic scaler which may induce similar thrombi formation within the pulpal or perapical tissues of the teeth. If this were to occur it could result in tooth death which might not become evident until a long time after the ultrasonic exposure.

Acoustics↗
PubMed1992

Evaluation of the CO2 laser for endodontic root apex welding.

A low-wattage carbon dioxide laser was tested as a means of welding (sealing) the apices of unfilled, endodontically prepared teeth. Thirty-five teeth were filed and lased using a variety of power settings. Apical seals were examined microscopically, radiographically, and mechanically for complete welds. Accurately directed laser exposures of 15 or more watts with a 0.5 second duration will completely seal the apical openings of anterior teeth. The ideal treatment for endodontically compromised teeth has always been a completely sealed tooth apex. Usually amalgam, gutta-percha, or resin sealers are used after a lengthy and tedious preparation of the exposed root area. The carbon dioxide laser is designed for soft tissue dental surgery but is capable of melting enamel and dentin which recrystallizes in a dense solid as it cools (fig. 1). The laser, with its potential for accurately delivering a great quantity of energy to a small, exposed surface, appears to be an excellent tool for quick, direct sealing of open apices. This paper will investigate the practicality and best methods of spot welding root apices.

Humans↗
PubMed1993

Histological techniques to improve testing of pulpal response of teeth to filling material.

Two fixation fluids, two fixation techniques and two embedding methods were investigated for their effects on the quality of sections of teeth for pulpal response to filling materials to improve evaluation of pulpal responses. Sections from 32 baboon teeth were prepared, half with experimental cavities and half without, using either 10% formaldehyde or 4% glutaraldehyde, longitudinal tooth splitting or removal of the tooth apex, and paraffin or K plast resin embedding; decalcification in a formic acid mixture was a constant throughout. Histometric analysis showed that paraffin embedding produced less shrinkage than the K Plast resin embedding although the difference was not statistically significant. Six parameters of separation at the pulp:dentine interface were studied: embedding, fixative, presence or absence of a cavity, cutting technique and individual animal tooth type. Statistical investigation revealed that fixative, cutting technique, and fixative and cutting technique combined had significant influences on the separation artifact. Of the combinations tested the choice of embedding method depends on which of the two artifacts, shrinkage or separation, is more adverse in the opinion of the investigator. Four percent glutaraldehyde together with the longitudinal split technique of fixation, processed by either K Plast resin embedding or paraffin embedding produced satisfactory pulpal sections.

Animals↗
PubMed1997

The buccal bifurcation cyst: a prospective study of treatment outcomes in 44 sites.

OBJECTIVE: The clinical, radiographic, and histologic features of the mandibular buccal bifurcation cyst were studied to further define this lesion. The treatment and outcomes were also analyzed. STUDY DESIGN: This prospective study, which spanned 3 years, included 32 patients. Their ages ranged from 5.5 to 11 years (mean of 7.5). A total of 44 buccal bifurcation cysts were treated solely with enucleation, and patients were followed up for 2.5 to 3 years. RESULTS: All lesions were located at the buccal bifurcation of the mandibular first molar. Tilting of the buccal cusps, causing prominence of the lingual cusps, occurred in 75% of the cases. The lesion extended from the buccal bifurcation to the tooth apex in 81.2%, and a periosteal reaction on the lateral surface of the mandible adjacent to the cyst was noted in 68.8% of the cases. All of the 44 histologic reports were nonspecific, but showed a cyst lining of stratified squamous epithelium with chronic inflammation. Microbiology consisted of mixed oral flora. Complete radiographic healing in all sites without recurrence was noted in 2.5-year follow-up. The periodontal pocket depth around all the involved teeth was normalized. No loss of the mandibular first molars occurred. CONCLUSIONS: The mandibular buccal bifurcation cyst is a distinct site-specific and age-specific clinical entity treatable by enucleation without tooth extraction.

Age Factors↗