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At least 955 records · Page 53Linked to original sources
PubMed1990

Genetic study on the mandibular molar size of rats.

Tooth size is determined by genetic and environmental factors like other quantitative characters such as body weight and body height. However, the degree of the relative contribution of both factors to the determination of tooth size has not been well clarified. In order to study the genetic and environmental factors affecting tooth size, we carried out a diallel cross mating by the cohabitation of pairs of males and females among 10 strains of rats. The bucco-lingual widths of the first, second, and third molars of the right mandible were measured in each offspring of F1 population. The body weight was also measured as a parameter that might indicate systemic growth factor in connection with tooth development. The quantitative genetic analysis was performed based on Wearden's model (Heredity 19:669-680, 1964). As a result, the size of the first and the second molars was more significantly controlled by genetic effect than maternal effect, while maternal effect could not be ignored for the size of the third molar in addition to genetic effect. The genetic effect on body weight became greater with age, while the maternal effect showed its maximum influence upon the body weight around the weaning. It is concluded that the size of the molar teeth beginning to develop in the uterus and to be calcified just after birth was mainly controlled by genetic factor, and that the size of the molar teeth beginning to develop approximately after birth was mainly controlled by maternal effect affecting body weight at the same period.

Animals↗
PubMed1979

Pattern formation in the molar dentition of the mouse.

The developing molar tissues of 10 to 16 day mouse embryos have been dissected from the lower jaws and cultured for periods of up to four weeks in the anterior eye chambers of homologous adult hosts. Grafts of 10 and 11 day presumptive molar tissues developed two complete tooth crowns identifiable as M1 and M2. Grafts of 12 day (dental lamina) and later stages produced similar results but in many cases all three molar teeth were developed, in their normal sequence and with normal crown shapes and proportions. From 12 days and probably earlier the complete molar dentition is represented by a discrete group of cells whose later growth and differentiation are already determined. The fact that individual primordia for the second and third molars are not yet present at this stage suggests that neither their appearance nor their normal differentiation in the jaws requires a morphogenetic gradient field, an extrinsic control which has been proposed and is often assumed to exist. The results are consistent with developmental theories which propose that gradations of shape and size in the individual sequentially initiated elements of a series are expressions of intrinsic time-dependent alterations in the growing cell population which forms them.

Animals↗
PubMed1979

[Fissure contents in rodent molars].

The fissure contents in rodent molars were examined by means of a stereomicroscope and compared with those in caries-free human molars and premolars. As to colour, consistency and removableness, the fissure contents in the rodent molars were similar to those in human teeth. An orange substance as found in the fissures of human teeth was not detected in the fissures of rodent molars. This fact does not tell against the use of rodent molars as a study model for fissure contents.

Animals↗
PubMedDate not supplied

[Edentation of the 6-year molar tooth. Clinical aspects and treatment].

The problem of the 6 year molar tooth edentation has been approached from an unilateral point of view. The present paper deals with the complex factors that contribute to the onset and evolution of the 6 year molar tooth edentation. The group studied included 2000 subjects making it possible to establish the frequency of the affection in terms of age, general condition of the body environmental factors, caries prevention, out-patient follow up, previous dental treatment. The study continued with 100 cases of molar edentation without prostheses, establishing the clinical and complementary signs of the 6 year molar syndrome. Likewise discussed are the favourable elements and errors in the concept and treatment of previously applied prostheses. A complex treatment was applied in 50 cases of 6 year molar edentation showing the preprosthetic, proprosthetic and prosthetic treatment applied and certain therapeutical techniques applicable by the practitioner.

Anodontia↗
PubMed1988

[Radiological estimation of interradicular space of primary molar teeth].

Radiological estimation of interradicular space of primary molar teeth has been performed. Radiograms taken from the department's archives on which primary molar teeth without dental caries were visible have been used for the purposes of the examinations. Roentgenograms had been made for exposition conditions required for endodontic therapy needs. Periodontium, lamina dura of the alveolus, bone texture of the interradicular space and disposition of permanent tooth buds have been estimated according to the radiograms. From the examination results it followed that proper estimation of interradicular space of primary molar teeth according to radiograms made for endodontic therapy needs is not possible. Radiological image of interradicular space of primary molar teeth in various both with reference to bone structure and disposition of permanent tooth buds. In most cases the interradicular space of primary molar teeth demonstrates thin bone structure on radiograms that should be considered to be physiological state when the continuity of lamina dura of the alveolus is preserved.

Humans↗
PubMedDate not supplied

Prenatal fluoride tablet supplementation and improved molar occlusal morphology: part V.

This article is a report of an in vivo clinical study in which the relationship of sodium fluoride supplementation during pregnancy to the improved occlusal morphology of molar teeth seen in an animal model was determined. Two hundred randomly selected children composed the study population. The mothers of 100 of them had been on the prenatal supplementation (PNF) regimen and 100 whose mothers were not were found to have statistically significant differences in their occlusal molar morphology. Ninety-eight percent of the PNF children have a smooth, naturally sealed appearance to the occlusal surfaces of their primary molars and permanent first molars. The authors conclude that pitted and fissured molars are produced as a result of fluoride deficiency during the secretory phase of crown formation.

Child↗
PubMedDate not supplied

Containing the cost of third-molar extractions: a dilemma for health insurance.

No known scientific studies support the extraction of third molars (wisdom teeth) to prevent future disease. Yet, third-molar surgery for this purpose has become so common that in at least one major U.S. health insurance plan, the cumulative cost exceeds that for every other kind of major surgery. Many third molars that are developing normally in adolescents are classified as impacted and removed before they erupt, a practice that results in large expenditures for unnecessary surgery. In addition, the difficulty of the extractions is frequently exaggerated, so that patients and insurance plans are overcharged. Third molar surgery is not without risk of iatrogenic injury. Fracture of the jaw, permanent numbness of the lip (paresthesia), and injury to other teeth may occur. This paper presents a mechanism for containing the cost of third-molar surgery by elimination of payment for nonessential extractions and of the related overcharges. Adoption of this policy by administrators of dental insurance plans would save millions of dollars each year, money that could be better used in providing care for more people with real dental disease.

Adolescent↗
PubMed1982

Histological and biochemical studies of vitamin C requirements of hamster molars during development in vitro.

The dose response relationship between medium concentrations of vitamin C (0-350 micrograms/ml) and the hydroxylation of in vitro incorporated 3H-proline showed that in (small) 2nd molars 50 micrograms/ml vit C at level of a maximum hydroxylation was attained at whereas in (larger) 1st molars higher medium concentrations seemed to be required (150 micrograms/ml or more). No cytotoxic effects were observed in media containing concentrations of vit C up to 350 micrograms/ml. In the absence of vit C odontoblasts in young 2nd molars failed to differentiate normally and an abnormal jelly-like substance was produced. Dentinogenesis in the 2nd molars was normal in the presence of at least 50 micrograms/ml vit C. In the 1st molars, in which production of collagenous dentine matrix had already started at the time of explantation, significantly less 3H-hydroxyproline was measured during vit C deficiency as early as the first day of culture, suggesting that there is a high need for vit C during dentinogenesis in vitro.

Animals↗
PubMed1995

[Fissure sealants versus fluorine varnish on the first permanent molars: economic assessment].

OBJECTIVE: To study school-children between the ages of 6 and 8 in order to make an economic comparison between two programmes aimed at preventing caries in the first permanent molars: sealants or fluorine varnish. DESIGN: A field trial over 24 months, with three groups of school-children (sealant/varnish/control). SETTING: Primary Care in the school environment (Granada). PATIENTS: 362 school-children between 6 and 8: 314 were followed for 24 months (100 sealant, 98 varnish and 116 control group). INTERVENTION: Sealant and fluorine varnish on the first healthy permanent molars, with weekly reapplications, using portable equipment. MEASUREMENTS AND MAIN RESULTS: The increase was measured over a 24-month period in both the DMFT (the total of the first permanent molars either with caries, missing because of caries or sedice filled) and the DMFS (DMFT, but referring to the surface) indexes. In relation to the DMFT, the effectiveness of the sealant (difference in increase of DMFT between the sealed and control groups) was -1.06 (Standard Error = 0.16) and of the varnish, -0.58 (SE = 0.18), which were statistically different figures. For DMFS, the effectiveness of the sealant was -1.83 (SE = 0.28) and of the varnish, 1.10 (SE = 0.33), also different. The costs per school-child did not differ sealant: 4,524 pesetas (SD = 1,248), and varnish: 4,373 (SD = 1,267). The cost/effectiveness ratio favored the sealant (4,268 pesetas per molar saved against 7,540). CONCLUSIONS: The sealant is more efficient (twice that of the varnish). The cost of saving a molar is 4,268 pesetas.

Case-Control Studies↗
PubMedDate not supplied

Orthodontic band retention on primary molar stainless steel crowns.

The retention of orthodontic bands cemented on primary molar stainless steel crowns (SSC) was studied in vitro. Unitek maxillary and mandibular 1st and 2nd primary molar SSC were fitted with one of four commonly used orthodontic bands (Unitek regular, Unitek narrow, Rocky Mountain, or custom bands made from SSC) using glass ionomer cement. The cemented samples were tested for their resistance to dislodgment on the Instron Universal Testing Machine (Instron Engineering Corp., Canton, MA) in tensile mode. Alpha level for statistical significance was set at alpha = 0.05. Unitek regular bands cemented on the 2nd molar crowns and Unitek narrow bands cemented on the 1st molar crown samples had equivalent or superior resistance to dislodgment compared with the other bands in the study. When the inside of the band and the outside band-bearing surfaces of selected crowns were lightly scored with a diamond bur prior to cementation, samples exhibited significantly superior retention. Subgroup means increased from 107 to 330%, compared to the values obtained in their preroughened state. The mean values obtained using the roughened band/crown interface technique (range 52.9 +/- 7.6 to 73.6 +/- 8.4 lbs) compared favorably with retention values from the literature for orthodontic bands cemented on permanent molar and premolar teeth.

Analysis of Variance↗
PubMed1993

Molar endodontics.

Molar endodontics is an extensive and complex subject. The treatment of molar teeth has deservedly taken a position of elevated importance in recent years. No longer are the molar teeth a target for extraction forceps, but are more often nowadays a target for crowns. Patients and dentists alike are striving to keep the marvellous molars and, with this in mind, the pillars of the future crowns and bridges must be preserved. Endodontic treatment of molar teeth is basically no different from treating the simple, single, straight canal. The principles of complete debridement, obturation and restoration are the same. The stumbling blocks confront us in the way of anatomical variations, difficulty with isolation and access and, probably the simplest and most crucial factor, time. Given the devotion of enough time, patience, and practice, the desired result will be achievable.

Crowns↗
PubMed1995

[Germectomy of the lower third molars. Follow up studies on 71 patients].

The clinical research was carried on in the department of Oral Surgery of the Maxillo-Facial Surgery Division of Turin University and concerned patients of an average age of 15 years. All the patients underwent the operation for orthodontic reasons. About two years after operation patients were called and underwent a check-up to see the surgical scar and to examine the health of lower second molars that could have been damaged during surgical operations for germectomy. Periodontal probings were effected around all lower second molars, therefore their mobility level an vitality were observed. Nervous alterations were researched and the authors effected a radiographic check-up to look for possible bone-loss after germectomy. According to the results obtained, the authors assert that the health of lower second molars isn't damaged by germectomy of lower third molars. So although not welcome by the young patients, the authors affirm that preventive germectomy of lower third molars compared to correct indications is a justified treatment.

Adolescent↗
PubMed1997

Evaluation of orthodontic treatment with early extraction of four second molars.

The outcome of orthodontic treatment involving early extraction of 4 second molars was evaluated in 52 patients (29 girls, 23 boys). Computer-assisted analysis of cephalograms, casts and panoramic X-rays was performed at the start (T1, mean age 11.5 years) and at the end (T2, mean age 14.4 years) of treatment. Following treatment, mesial migration of upper and lower first molars was counteracted; however, treatment only moderately influenced normal development of the position of the incisors and the profile. At the end of treatment, the third molars had erupted in only 3 patients. Nevertheless, on average a significant mesial movement of these teeth was observed. In addition, there was a significant improvement in the axial inclination of the third molars, especially in the upper arch. This improvement was correlated with the original position of the teeth. All patients needed a longer follow-up period and it seems reasonable that some of them might require a second treatment phase to adjust the position of the third molars.

Adolescent↗
PubMedDate not supplied

Infraclusion of primary molars: reports of cases.

A review of twenty-five patients (nine boys and sixteen girls with a mean age of 13.6 years) with infraclusion of primary molars is reported. There were thirty-two infracluded teeth, twenty-one (65.6 percent) maxillary primary molars and eleven (34.4 percent) mandibular primary molars. The primary first molar was found to be in infraclusion in four (12.5 percent) cases and the primary second molar in twenty-eight (87.5 percent) cases. Submergence was mild in fifteen cases, moderate in five, and severe in twelve. The permanent successor was lacking in four (12.5 percent) infracluded teeth. Aplasia of a nonsuccedaneous tooth was observed in four patients (more than one aplasia in three of them). Sixty-five percent of the teeth distal to the infracluded tooth had some degree of mesioversion, and 34.4 percent showed a distoversion of the mesial tooth. Twenty-one patients underwent orthodontic therapy because of malocclusion induced by the submerged tooth or for other reasons. A total of twenty-five (78.1 percent) teeth had to be extracted (surgical extraction in seventeen cases). An alveolotomy made to help the succedaneous tooth to erupt was necessary in ten cases.

Adolescent↗
PubMed1998

Orthodontic treatment planning for inclusion of the third molar in the dental arches: Part II.

Marked lower anterior crowding (late crowding or post-adolescent crowding) often develops at about the time of third molar eruption. Many studies have implicated the presence of third molars as a cause of this crowding. Despite the fact that there is no clear evidence that this is the case, many orthodontists and their patients' referring dentists routinely remove third molars at the retention stage of treatment to prevent crowding later; Ricketts et al. even advocate enucleation of the third molar while the patient is very young to prevent future crowding. In the following report on two orthodontically-treated patients (the first three cases in this report were published in The Australian Orthodontic Journal, Volume 15, Number 1), the author emphasises the importance of careful consideration of the third molar in the treatment plan.

Adolescent↗
PubMed1998

[Postoperative follow-up after extraction of an impacted lower third molar].

BACKGROUND: On the basis of an anatomo-surgical classification adopted in our Department, that divides impacted lower third molars into (1) ectopic, (2) dystopic and (3) in the proper anatomical site, and the latter into Class A (complete bone impaction without pathology of the second molar), Class B (mucosal impaction with pathology of the second molar: Subclass B1, if the mucosa distal to the second molar is of a normal amount; Subclass B2, if the retromolar mucosa is plentiful), and Class C (mucosal semi-impaction), the authors carried out a comparative study on 20 patients who underwent extraction of both Class C lower third molars. METHODS: These operations were performed, in each patient, on one side raising an Archer's flap and on the other introducing a modification of the incision lines using Z-plasty for flap design. The patients were examined from the first postoperative hours up to the 7th day following a protocol aimed at monitoring the postoperative variables pain, edema, trismus, infection and healing time. RESULTS AND CONCLUSIONS: The preliminary results, analyzed by Student's "t"-test, are statistically significant (p < 0.05), and favour the hypothesis that the technical modification proposed for the flap, by permitting a better closure of the socket, involves a lesser incidence of postoperative complications and in any case a more comfortable postoperative course.

Adult↗
PubMed1998

"9-year-molars" aberrantly developing and erupting: report of cases.

This paper describes delayed development and eruption of the first permanent molars, in most cases only in the upper jaw. The development and eruption of the teeth are chronologically between that of the first and second molars. The anatomy of the aberrant teeth is closest to that of the second molars. The aberrant teeth are often laying at a distance during development from the second primary molars. The clinical implications of the aberrancy are few, because the teeth will normally migrate into close contact with the tooth mesial to them, however, often into a crossbite. Most often the teeth are mistaken to be a first molar with some eruption disturbance and therefore referred for surgical or orthodontic treatment. However, such interception should be avoided because at least in the present cases all teeth are observed to erupt by themselves.

Anodontia↗
PubMedDate not supplied

Use of wide-diameter and standard-diameter implants to replace single molars: two case presentations.

PURPOSE: The ultimate goal in modern esthetic dentistry is the restoration of lost hard and soft tissues by imitating nature as closely as possible. With the increasing esthetic awareness of patients, surgical and technical developments, and dentists' enhanced skills and knowledge, optimal function and esthetics are achievable even with implant-supported restorations in molar regions. Anatomic and morphologic factors and poor bone quantity and quality might reduce success rates of dental implants in the posterior jaw. Today, there are two options to replace a single missing molar by an implant-supported crown: the single wide-diameter implant or two standard-diameter implants. These two approaches are described and their advantages and disadvantages discussed in two exemplary clinical cases. MATERIALS AND METHODS: In one case, the edentulous ridge in the area of the mandibular right first molar (FDI tooth 46) provided sufficient mesiodistal space to restore tooth 46 with a porcelain-fused-to-metal crown on two standard-diameter implants, placed in a root-analog manner. In the other case, the manibular first molars (FDI teeth 36 and 46) were replaced by porcelain-fused-to-metal crowns on wide-diameter implants. RESULTS: It can be concluded that both options to replace a single molar provide more surface area and better biomechanical properties than one standard implant. CONCLUSION: Long-term data are needed before these treatment modalities can be recommended for the private practitioner.

Adult↗