Efficacy of CO lasers in preventing dental caries in partially erupted first permanent molars: a randomized 18-month clinical trial.

The aim of this controlled randomized double-blinded clinical trial was to evaluate the use of a CO2 laser with or without topical application of acidulated fluorides in the prevention of dental caries in partially erupted first permanent molars. We selected 61 healthy children at high risk of caries, all between 6 and 8 (7.1 ± 0.8) years of age and with 4 partially erupted first permanent molars. A CO2 laser device emitting at 10.6 µm was used (0.5 W, 0.05 mJ per pulse, 10 kHz). Each first molar in an individual was randomly assigned to one treatment: (L) CO2 laser (0.066 J/cm2); (FL) 1.23% acidulated fluoride gel and CO2 laser (0.066 J/cm2); (V) 5% fluoride varnish, or (S) sealant (control). Patients were followed-up at 3, 6, 12, and 18 months after treatment, through direct visual examination and by an operator blinded to the treatments (kappa ≥ 0.70). The International Caries Detection and Assessment System (ICDAS-II) index was used to assess the soundness of tooth structure or the presence of white spot lesions, cavitated enamel, and/or dentin lesions. The Yildiz Visual Index was used to evaluate sealant retention. Results were evaluated using Kaplan-Meier survival analysis, and the hazard ratio of the treatments was estimated using shared frailty models with a gamma distribution, which considered the patient as a cluster. There were no significant differences among treatments compared to sealants. After 18 months, the use of a CO2 laser with or without acidulated fluorides was shown to be effective in preventing caries on the occlusal surface of partially erupted permanent first molars in children at high risk for caries.

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Anatomical characteristics and visibility of mental foramen and accessory mental foramen: Panoramic radiography vs. cone beam CT

BACKGROUND: The mental foramen (MF) is a small foramen located in the anterolateral region of the mandible through which the mental nerve and vessels emerge. The knowledge on the anatomic characteristics and variations of MF is very important in surgical procedures involving that area. The aim of this study was two-fold: firstly, to analyze the anatomic characteristics of MF and the presence of accessory mental foramen (AMF) using CBCT and, secondly, to compare the capability of CBCT and PAN in terms of MF and AMF visualization, as well as influencing factors. MATERIAL AND METHODS: A sample of 344 CBCT scans was analyzed for presence and characteristics (i.e. diameter, area, shape, exit angle) of MF and AMF. Subsequently, corresponding PANs were analyzed to ascertain whether MF and AMF were visible. RESULTS: Out of the 344 patients, 344 (100%) MFs and 45 (13%) AMFs were observed on CBCT. Regarding gender, MF diameter and area, MF-MIB and MF-MSB distances, and exit angle were all significantly higher in males. Also, statistically significant differences were found in terms of age and dental status. Statistically significant differences in MF long and short diameters and MF area were found with respect to AMF presence (p=.021, p=.008, p=.021). Only 83.87% of the MFs and 45.83% of the AMFs identified on CBCT were also visible on PANs. MF diameter, shape, exit angle, and age had a significant influence on MF visualization on PAN (B=.43, p=.005; B=-.55, p=.020; B=.20, p=.008; B=.61, p=.005). CONCLUSIONS: PAN is not an adequate technique to properly identify MF and AMF. Diameter, shape, exit angle, and age are all factors influencing MF visualization on PAN images. For surgery involving the MF anatomical region, a preoperative radiological study with CBCT is of crucial importance to avoid complications

Effect of radiotherapy on the eruption rate and morphology of the odontogenic region of rat incisors.

OBJECTIVE: The goal in this study was to evaluate the results of doses of 5 and 15 Gy of radiation in odontogenic region of the rats inferior mandibular-incisors by a histological analysis and the rate of eruptions. DESIGN: Animals were divided into three groups: control, radiotherapy 5 Gy and radiotherapy 15 Gy. In which tooth-eruption-rate was measured every two days. RESULTS: Animals in Group 5 Gy presented values similar to those of the control group. Animals in Group 15 Gy presented reduction in tooth-eruption-rate as of the sixth day of the experiment, vast disorganization of odontoblasts and ameloblasts, apparent reduction in cell population in the follicle region and alterations in cervical loop formation of the dental organ. CONCLUSIONS: It was concluded that there was a difference between the researched doses, and histological alteration at 15 Gy lead to statistical reduction in tooth-eruption-rate.

Prevention of third molar development in dog with long pulse diode laser: a preliminary report.

INTRODUCTION: Wisdom teeth continue to plague man with a high rate of frequency. It may be possible to prevent their development in children at an early age with a non- or minimally invasive technique, even before the tooth begins to form, by treating the soft tissue overlying the site of their development. A previous study that treated the intra-oral soft tissues of newborn rats with a 20 watt diode laser stopped third molar development up to 80% of the time with minimum observable side effects. This brief report describes a similar use of the diode laser in a limited number of young beagle pups. It is the first reported attempt at preventing third molar development in an animal model close in size to man. MATERIALS AND METHODS: Four 6-7 week old beagle pups were treated on one side of their mandibles with either a 20 or a 100 watt, 800 nm diode laser at a time third molar tooth buds are just beginning to form under the oral mucosa. Six months following treatment, the pups were examined intra-orally and radiographically for evidence of third molar formation. RESULTS: The two intra-oral sites that received the 20 watt diode laser treatment showed normal third molar development. The two intra-oral sites that received the 100 watt diode laser treatment did not develop third molars. CONCLUSIONS: The diode laser may be capable of selectively stopping third molar development and further studies are warranted.

Catch-up of delayed tooth eruption associated with uranium intoxication.

The population at large is at risk of oral exposure to uranium. Previous studies performed at our laboratory showed delayed tooth eruption 7 d post-administration of a single oral dose of uranyl nitrate in newborn rats. Rat kidney exhibiting severe damage 2 d post-acute uranyl nitrate exposure showed signs of recovery after 7 d; however, tooth eruption and development were significantly lower as compared with their age-matched controls. The aim of the present work was to establish whether tooth eruption and development, delayed by uranium exposure, can catch up to normal values at longer experimental times. In addition, since it is well documented that uranium intoxication by other routes of entry causes alterations in bone growth, we also aimed to evaluate the effect of oral exposure to uranium on mandibular growth. An experimental group of 16 1-d-old Wistar rats received a single 90 mg kg-1 body weight oral dose of uranyl nitrate. Another group of 16 age-matched rats received an equal volume of saline solution and served as the control. Eight animals in each group were killed 7 d post-treatment, and the remaining animals were killed 27 d after the onset of the experiment. Morphometric measurements of mandibular growth were performed on radiographs. Tooth eruption and development were evaluated histomorphometrically on histologic sections obtained at the level of the mesial root of the first molar. Our results showed that the tooth eruption, dental development, and mandibular growth retardation observed 7 d post-acute uranyl nitrate exposure caught up completely after 27 d.

Pulsed Nd:YAG laser effect on eruption of rat mandibular incisors following disturbance of the enamel organ in the pulp.

We investigated the effects of pulsed neodymium:yttrium-aluminium-garnet (Nd:YAG) laser irradiation time on the eruption of 56 mandibular incisors in 28 rats. Clinically, some incisors erupted and the others did not. The incisors were irradiated at 2 W, 20 pulses/s for the period of 3 s, 5 s, 7 s, and 10 s, and the regeneration process was monitored at 20 days after laser treatment. Incisors irradiated for 3-5 s continued their eruption; five incisors irradiated for 7 s and all incisors irradiated for 10 s did not erupt. In the incisors that continued to erupt, the inner epithelial cells differentiated into ameloblast and a part of the pulp cavity was occupied by osteodentin. In the teeth in which eruption had ceased, the inner epithelium cells did not differentiate into ameloblast, and most of the pulp cavity was occupied by osteodentin. The results indicate that a relatively short time duration of pulsed Nd:YAG laser irradiation in the pulp induced the reparative process without disturbing the eruption.

Prevention of third molar tooth development in neonate rat with a long pulse diode laser.

BACKGROUND AND OBJECTIVES: Third molars (wisdom teeth) in humans have limited functional value and cause a high frequency of morbidity. A window of opportunity exists to stop their development. The purpose of this study is to evaluate whether a long pulse diode laser can selectively prevent third molar development in a rat animal model. STUDY DESIGN/MATERIALS AND METHODS: The study calculated theoretical diode laser parameters and irradiated 2- to 4-day-old rat pups in the posterior aspects of the oral cavity near the time of tooth bud initiation. Rats were sacrificed at 35-50 days and examined intraorally and radiographically for third molar development. Control and treated sides were compared histologically. RESULTS: Nearly half of the maxillary third molars and 80% of the mandibular third molars were selectively prevented from developing using a 20 W diode laser with infrequent, minor adverse effects on maxillary jaw growth. CONCLUSIONS: This study confirms the hypothesis that controlled, non-invasive laser treatment delivered on the surface of the oral mucosa near the site of tooth bud formation can selectively achieve third molar agenesis. It also offers hope that further innovative studies may bring about a safe, non-invasive laser treatment to selectively prevent third molar development in humans.

Exposure to oral uranyl nitrate delays tooth eruption and development.

The risk of oral exposure to uranium potentially involves the population at large. Tooth eruption and development are ongoing processes that begin during fetal development and continue until the age of 18 y. Since one of the mechanisms involved in tooth eruption is bone formation and it is well documented that uranium inhibits bone formation, the aim of the present work was to study the effect of oral administration of uranyl nitrate (UN) on tooth eruption and development. Wistar rats aged 1 and 7 d were orally administered a single dose of 90 mg kg(-1) body weight of uranyl nitrate. Two age matched groups received an equal volume of saline and served as controls. The animals were killed at 7 and 14 d of age, respectively. Mandibles were resected and processed to obtain bucco-lingual sections oriented at the level of the mesial root of the first mandibular molar, and histomorphometric studies were performed. Results showed that an acute high dose of uranyl nitrate delays both tooth eruption and development, probably due to its effect on target cells.

Dental abnormalities in children after chemotherapy treatment for acute lymphoid leukemia.

The frequency of dental abnormalities, such as delayed dental development, microdontia, hypoplasia, agenesis, V-shaped root and shortened root was evaluated in 76 acute lymphoblastic leukemia (ALL) pediatric patients who had been off chemotherapy for 6 months. These children had been subjected to one of the three Brazilian Protocols or the BFM86 Protocol. The patients were divided into three groups: Group I (GI; high risk) treated with one of the three Brazilian Protocols who received high-dose chemotherapy, intensive maintenance and cranial radiotherapy; Group II (GII; low risk) who were also treated with one of the three Brazilian Protocols using low-intensive chemotherapy with no radiotherapy; and Group III (GIII) based on the BFM86 Protocol. Of 76 children, 13 showed no dental abnormalities (8 were at the age of tooth formation). The remaining 63 children (82.9%) showed at least one dental anomaly. The abnormalities were probably caused by the type, intensity, frequency of the treatment and age of the patients at ALL diagnosis and this might have important consequences for the children's dental development.

An immunohistochemical study of the effects of pulsed neodymium:yttrium-aluminium-garnet laser irradiation in root canals on the eruption of rat incisors.

The incisors of 21 Wistar rats were transected, pulp tissue was extirpated for 10mm from the level of the gingival margin and each canal was prepared with files. The fibre tip of a pulsed neodymium:yttrium-aluminium-garnet laser was inserted into the root canal for 10mm and laser irradiation delivered at 2 W and 20 pulses/s for 10s. After 6 weeks the mandibles were removed and sectioned. Sections were stained either with haematoxylin and eosin or immunohistochemically using polyclonal antibodies against keratin/cytokeratin, amelogenin and type I collagen. The inner epithelial cells on the labial side differentiated into ameloblasts in animals where eruption had recovered. The pulp cells differentiated into odontoblast-like cells and staining for type I collagen was evident in pulp cells, odontoblast-like cells and inside dentinal tubules. In animals where eruption had ceased, the inner epithelial cells on the labial side did not differentiate into ameloblasts. Staining for type I collagen was observed in the mineralized nodules and tubules of dentine-like hard tissues in the pulp cavity. These results suggest that differentiation of epithelial cells on the labial side into ameloblasts is involved in the re-eruption process.

[The time periods for the formation of the permanent occlusion in children born and permanently living in a region close to a former nuclear test range]. / Sroki formirovaniia postoiannogo prikusa u detei, rodivshikhsia i postoianno prozhivaiushchikh v regione, nakhodiashchemsia vblizi byvshego iadernogo poligona.

The terms of eruption of permanent teeth were analyzed in 2000 subjects aged 3-19 years born and permanently living in a region adjacent to a former nuclear testing field in Kazakhstan. All groups of permanent teeth erupted sooner, and the rate of eruption was higher in girls than in boys. Except the 4th and 5th teeth, all groups of permanent teeth erupted sooner on the mandible than in the maxilla. The formation of occlusion was delayed in children born and living in the studied region in comparison with the children in central Russia and in the Extreme North. Eruption of some groups of teeth was delayed in older age groups. These data may be used at all pedodontics departments in organization of sanitation of children and in evaluation of the physical development and formation of orthodontic status of children.

Physical and motor development in male and female rat offspring prenatally exposed to gamma radiation.

The effects of radiation on physical and motor development of male and female rats exposed to ionizing radiation in utero were studied. Rats were exposed to three different doses of radiation (150 rad, 15 rad and 6.8 rad, considered as high, moderate and low doses of radiation respectively) on the 20th day of prenatal life. Exposure to 150 rad contributed to significantly lower body weights of both male and female rat offspring. Upper jaw tooth eruption was delayed in 150 rad treated male offspring, as well as in 15 rad and 150 rad treated female offspring. Cliff-avoidance response was delayed in 6.8 rad, 15 rad, and 150 rad treated male offspring; and 150 rad treated female offspring. Lower jaw tooth eruption, eye opening, and crawling were not affected by radiation in male or female animals. Results indicate that radiation affected the developmental parameters of both male and female rat offspring, and sex of the offspring played no role in the magnitude of radiation induced damages.

Impairment of molar tooth eruption caused by x-radiation.

The effect of x-radiation on erupting molars is presented. New born, 5 day old Wistar rats were locally irradiated in the molar area with doses of 20 Gy. They were killed in two groups, 30 and 60 days postirradiation respectively. Two other groups of non irradiated, age matched rats were killed at the given times. In addition a control group of 5 day old animals was also studied. Radiographic and histologic studies were performed. Odontoblastic atrophy, odontodysplasia, rootless formation, and ankylosis of tooth to bone by osteodentin formation with the resulting lack of tooth eruption were observed. The relation between the histologic alterations and tooth eruption is discussed.

Micrognathia after radiation therapy for childhood facial tumors. Report of two cases with long-term follow-up.

As the survival duration and cure rate of children with malignant conditions improve, awareness of long-term side effects is crucial. Two case reports demonstrate long-term changes in dentition and orofacial development in children who had been treated for facial malignant conditions. Changes induced mandibular and maxillary hypoplasia, partial anodontia, microdontia, altered eruption pattern, root stunting, and altered amelogenesis.

Effects of prenatal exposure to 50 Hz magnetic fields on development in mice: II. Postnatal development and behavior.

To investigate the potential of magnetic fields to act as a behavioral teratogen, pregnant CD1 mice were exposed or sham-exposed for all of gestation to a 50 Hz/20 mT magnetic field. Maturation of offspring was assessed using a range of standard developmental indices (eye opening, pinna detachment, hair coat, tooth eruption, sexual maturity, and weight) and simple reflexive behaviors (air righting, surface righting, forepaw grasp, cliff avoidance, and negative geotaxis). Activity and coordination levels were explored in juvenile and adult mice using an open field arena, a head-dip board, an accelerating Rotarod, and a residential activity wheel. All assessments were carried out without knowledge of exposure condition. Results from 168 sham-exposed mice from 21 litters and from 184 exposed mice from 23 litters were compared using survival analysis techniques and multivariate regression methods. Three possible field-dependent effects were found: Exposed animals performed the air righting reflex earlier (P < 0.01); exposed males (but not females) were significantly lighter in weight (P = 0.008) at 30 days of age; and exposed animals remained on a Rota-rod for less time as juveniles (P = 0.03). Some of these results have not been reported in other studies and may reflect spurious statistical significance, although some effect of magnetic field exposure cannot be ruled out. Overall, these results suggest that prenatal exposure to a 50 Hz magnetic field does not engender any gross impairments in the postnatal development or behavior of mice. This does not preclude such exposure affecting more subtle aspects of behavior.

Histologic changes in dental morphology induced by high dose chemotherapy and total body irradiation.

Disturbances in dental development were studied with the use of radiography and histology in a patient with acute lymphoblastic leukemia who was treated with induction chemotherapy at 2.3 years of age and bone marrow transplantation at 4.3 years of age. The follow-up 9.5 years after bone marrow transplantation showed evidence of short tapered roots, enamel hypoplasia, microdontia, and aplasia. A histologic examination of two extracted permanent teeth showed that the crown of the maxillary lateral incisor exhibited numerous incremental lines that corresponded closely to the treatment periods with cytotoxic drugs. The maxillary second premolar exhibited regularly spaced incremental lines in the enamel and dentine. A gross hypoplasia was seen in the cervical part of the crown corresponding to the time of administration of 10 Gy total body irradiation. The results indicate that chemotherapy mainly induces qualitative disturbances in dentine and enamel, whereas total body irradiation induces both qualitative and quantitative changes.

Locomotion and physical development in rats treated with ionizing radiation in utero.

Effects of ionizing radiation on the emergence of locomotor skill, and physical development were studied in laboratory rats (Fisher F-344 inbred strain). Rats were treated with 3 different doses of radiation (150 rad, 15 rad, and 6.8 rad) delivered on the 20th day of prenatal life. Results indicated that relatively moderate (15 rad) to high (150 rad) doses of radiation had effects on certain locomotion and physical development parameters. Exposure to 150 rad delayed pivoting, cliff-avoidance, upper jaw tooth eruption, and decreased body weights. Other parameters, such as negative geotaxis, eye opening, and lower jaw tooth eruption were marginally delayed in the 150 rad treated animals. Exposure to 15 rad delayed pivoting and cliff-avoidance.

The physiological effects of radiotherapy on oral tissue.

An increasing number of head and neck cancer patients are undergoing radiotherapy along or in conjunction with other treatment modalities. Radiotherapy extending over a period of weeks produces a variety of clinical manifestations. This article discusses the physiological changes that occur due to radiotherapy to elucidate the changes seen clinically.

Mandibular growth and tooth eruption after localized x-radiation.

The effect of localized x-radiation on the growth of mandibular bone and molar eruption was evaluated by morphometric methods. A dose of 20 Gy of x-radiation was given to the molar zone of growing rats. The animals were then killed in groups at 30 and 60 days postirradiation. Two groups of nonirradiated, age-matched rats were used as controls. Parameters related to molar eruption, mandibular length, and mandibular height were measured on lateral radiographs. The results obtained showed that the values of the biometric parameters were lower in experimental than in control animals. Odontoblastic atrophy, alveolodentary ankylosis, and meager or no root formation were the most conspicuous histologic findings. Osteodentin was found between canaliculary dentin and bone in cases of ankylosis. The morphometric data presented confirm the probability of alterations in mandibular growth and tooth eruption following x-radiation and suggest that this be considered in planning radiotherapy in children.