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At least 865 records · Page 48Linked to original sources
PubMed2005

The Relationship between molar dentoalveolar and craniofacial heights.

Excessive vertical growth of the posterior dentoalveolar region has been implicated in the etiology of the so-called long-face syndrome. In this study, we tested the hypothesis that molar dentoalveolar heights are positively related to vertical craniofacial features. Cephalometric measurements obtained from 82 adult subjects were entered as independent variables in a multiple regression model. Maxillary and mandibular molar dentoalveolar heights were entered as dependent variables. Approximately 70% of the total variance was explained by anterior lower facial height (ANS-Me) and the mandibular palatal plane angle (PP-MP). Increases of ANS-Me and PP-MP had opposite effects on the amount of molar dentoalveolar heights. The lowest values of molar dentoalveolar heights were found in subjects with a small ANS-Me distance but with a wide PP-MP angle. The findings suggest that individuals with a marked divergence of the jaws may also have a reduced molar dentoalveolar vertical development.

Adolescent↗
PubMed2006

Noncompliance unilateral maxillary molar distalization:.

The aim of this prospective study was the three-dimensional (3-D) analysis of tooth movements after unilateral upper molar distalization by means of a noncompliance intraoral appliance, the Keles slider. This appliance exerts a distalizing force of 150 g at approximately the level of the center of resistance of the upper first molar. Twelve patients (six girls and six boys with a mean age of 13.1 years) with a unilateral Class II molar relationship participated in the study. Dental casts were taken immediately before placement and after removal of the appliance. The casts were digitized using a 3-D surface laser scanner and superimposed on a predefined area of the palate. The average unilateral upper first molar distal movement was 3.1 mm (range: 2.4 to 5.3 mm). Anchorage loss was expressed by a 2.1 mm (range: 0.8 to 3.8 mm) proclination of the central incisors and a 6.1 degrees mesial inclination of the ipsilateral first premolar (range: 1.7 degrees to 12.3 degrees ). There was approximately 1 mm of midline deviation toward the contralateral side and a 1.6 mm (range: 0.8 to 2.3 mm) buccal displacement of the contralateral first premolar. A substantial variation was observed among patients. Noncompliance unilateral upper molar distalization was an efficient treatment approach. There was, however, a substantial anchorage loss. Case selection is strongly recommended because significant anterior crowding, ectopic canines, or spacing can lead to significant anchorage loss.

Adolescent↗
PubMed2004

The interrelationship between bolus breakdown, mandibular first molar displacement and jaw movement during mastication.

The purpose of this study was to clarify the interrelationship between food bolus breakdown, mandibular first molar displacement and jaw movement during mastication. Finite element models were constructed of the maxillary first molar crown, the mandibular first molar consisting of crown, root, periodontal ligament and alveolar bone, as well as the food bolus were constructed. Based on the actual measurement of the jaw movement pattern and the characteristics of food bolus, the patterns of mandibular first molar displacement and bolus breakdown on time course in the progress of mastication were simulated, to investigate the biomechanical significance of tooth displacement and jaw movement during mastication, using finite element non-linear dynamic analysis. The results showed that the patterns of tooth displacement and jaw movement and characteristics of food bolus changed with an interrelationship to each other as mastication progressed. Particularly at the initial phase, it was suggested that the patterns of mandibular first molar displacement and jaw movement worked inter-dependently to accomplish an efficient hard-bolus breakdown.

Adult↗
PubMed2002

Root and canal morphology of Thai mandibular molars.

AIM: To investigate the root and canal morphology of 351 mandibular permanent molars collected from an indigenous Thai population. METHODOLOGY: The cleaned teeth were accessed, the pulp dissolved by sodium hypochlorite under ultrasonication and the pulp system injected with Indian ink. The teeth were rendered clear by demineralization and immersion in methyl salicylate. The following observations were made: (i) number of roots and their morphology; (ii) number of root canals per tooth; (iii) number of root canals per root; (iv) root canal configuration in each root using Vertucci's classification, with additional modifications; and (v) presence and location of lateral canals and intercanal communications. RESULTS: Of 118 mandibular first molars, 13% had a third disto-lingual root. In three-rooted teeth, 80% of the main distal roots and 100% of the disto-lingual roots had type 1 canal systems. Of 60 mandibular second molars, 10% had C-shaped roots, the majority of which had type 1 (33%) or type IV (33%) canal systems. Of 173 third molars, 68% had two separate roots, 20% had fused roots and 11% had a single C-shaped root; the majority had two canals (61%). CONCLUSIONS: This study suggests that Thai molars exhibit features of both Caucasian and Chinese teeth.

Asian People↗
PubMed2002

C-shaped root canals in mandibular second molars in a Saudi Arabian population.

AIM: The aim of this study was to determine the frequency of C-shaped canals in mandibular second molars in a population in Saudi Arabia and to establish a classification for the most common configurations. METHODOLOGY: One hundred and fifty-one mandibular second molars scheduled for root-canal treatment were examined over a 1-year period. The C-shaped canals were detected by radiographic and clinical examination. Teeth with C-shaped canal systems were categorized by using a modification of the classification of Melton. RESULTS: Of the 151 molars, 16 (10.6%) exhibited C-shaped canals. Five molars were classified as category I, and three were considered category II. The remaining eight cases were classified as category III, with two in subdivision I, two in subdivision II, and the remaining four in subdivision IIL. CONCLUSIONS: The C-shaped canals in mandibular second molars vary considerably in their anatomical configuration with the result that debridement, obturation, and restoration may be difficult.

Arabs↗
PubMed1998

A clinical and radiographic study of 25 autotransplanted third molars.

This paper is a report on 25 autotransplantations of third molars with complete root formations. The study consists of 23 patients in whom 25 third molars were transplanted. The mean age was 29.6 years (range 20-54). In nine cases third molars were directly transplanted into the new socket. In 11 cases the sockets were widened and made deeper with a bur. In five cases the recipient beds were made by splitting osteotomy of the alveolar region. The transplanted third molars were stabilized with silk sutures, resin, wire splint or circumferential wiring for 1-6 weeks. Two-three weeks after transplantation, the root canals were treated and filled. After operation, the marginal and the periapical conditions were examined clinically and radiographically. The transplanted teeth clinically appeared to become firmer with the passage of time. Progressive root resorption was not found and good results were obtained. This study shows that autotransplantation of third molars with complete root formation produces an acceptable result using the procedures outlined.

Adult↗
PubMed2003

Recovery after third molar surgery: clinical and health-related quality of life outcomes.

PURPOSE: The study goal was to assess both clinical and health-related quality of life (HRQOL) outcomes after third molar surgery. METHODS: Patients who were having 4 third molars removed were enrolled in a prospective clinical trial. Baseline data were recorded that included demographics, the patient's and surgeon's assessment of third molar conditions, and details of the surgical procedure. After surgery, clinical data were collected that detailed healing and any treatment that was rendered. Each patient was given an HRQOL instrument to complete on each postsurgery day for 14 days; the instrument was designed to assess a patient's perception of recovery in 4 main categories: pain, lifestyle, oral function, and other symptoms related to the procedure. RESULTS: Recovery data were available for 630 of 740 enrolled patients. The median age of the 630 patients was 21 years, and the median operation time was 30 minutes. Recovery for most HRQOL measures occurred within 5 days after surgery. However, recovery from pain to the criterion of "little or none" was delayed relative to other HRQOL measures. Twenty-two percent of patients were treated for delayed healing after surgery. CONCLUSIONS: Having both clinical and HRQOL data on recovery after third molar surgery could assist the surgeon when informing prospective patients about what to expect after surgery to remove third molars.

Adult↗
PubMed2000

Influence of orthodontic treatment on development of third molars.

We aimed to find out whether extraction of lower premolars and subsequent closure of the space by a fixed appliance influenced the chances of mandibular third molars erupting. We compared angular and linear measurements of lower third molars on dental panoramic tomograms in 30 orthodontic patients with similar measurements from 30 patients with impacted third molars in intact arches. We found that the mesial angulation of lower third molars was reduced from 50 degrees to 43 degrees by orthodontic treatment (P< 0.001). Distance to the occlusal plane was reduced from 12 mm to 10 mm (P< 0.001). The space available increased from 4 mm to 11 mm (P< 0.001). We conclude that extraction of lower premolars and orthodontic treatment to achieve complete closure of the space allowed the positions of many impacted lower third molars to improve significantly.

Adolescent↗
PubMed2001

Anatomic position of the lingual nerve in the mandibular third molar region with special consideration of an atrophied mandibular crest: an anatomical study.

The position of the lingual nerve in the mandibular third molar region was measured and documented in 68 cadaver dissections (34 adult cadaver heads). In 8.8% of the dissections, the lingual nerve was found at or above the level of the alveolar crest. In the horizontal plane, the nerve contacted the lingual plate of the third molar in 57.4% of the specimens. There was also a significant relationship between the degree of mandibular crest atrophy and the distance from the nerve to the molar region. The distance decreased with the degree of atrophy. There was no significant difference between the two sides of the head. These results demonstrate the vulnerability of the lingual nerve as it medially passes the mandibular third molar and may help avoid lingual damage during surgery in the third molar and retromolar region of the mandible.

Aged↗
PubMed2000

Expression of amelin and amelogenin in epithelial root sheath remnants of fully formed rat molars.

OBJECTIVE: To study the expression patterns of 2 enamel proteins, amelin and amelogenin, in the epithelial cells of the root sheath of fully formed rat molars. STUDY DESIGN: Twelve Sprague-Dawley rats, 50, 65, and 85 days of age, were used in this study. The maxillae of the rats were dissected free, and sagittal serial sections were made through the mesial root of the first molar. In situ hybridization of amelin and amelogenin mRNAs was performed, and immunohistochemical examinations of the corresponding proteins in the epithelial cells of the root sheaths of fully formed rat molars were performed. Antibodies against epidermal keratins were used to identify epithelial root sheath remnants. RESULTS: A group of epithelial cells, enclosed at the border between cellular cementum and dentin, expressed and synthesized amelin, but not amelogenin. Another group of epithelial cells, forming islands or strands, which were partially or totally incorporated in the matrix of the cellular cementum, expressed and synthesized both amelogenin and amelin. A third group of epithelial cells at the periphery of the cellular cementum expressed neither of the 2 proteins. Epithelial cells at the surface of acellular cementum did not express either of the 2 proteins. CONCLUSION: This study showed that the epithelial root sheath remnants in rat molars express and synthesize amelogenin, as well as amelin. However, there are marked regional differences. The roles of the enamel proteins in the formation of the radicular hard tissues of the rat molars and in the maintenance of the periodontal tissues remain to be clarified.

Amelogenin↗
PubMed2001

Inferior alveolar nerve damage after lower third molar surgical extraction: a prospective study of 1117 surgical extractions.

PURPOSE: The purpose of this study was to determine the incidence of inferior alveolar nerve (IAN) damage after surgical removal of lower third molars, to identify the causes, and to construct a predictive model to assess the risk of IAN injury. STUDY DESIGN: We performed a nonrandomized forward prospective study of 946 consecutive outpatients subjected to surgical extraction of 1117 lower molars in the University of Barcelona Oral Surgery Department. Preoperative, intraoperative, and postoperative data were gathered, and suspected causal factors of IAN damage were identified by using nonparametric tests, the Pearson chi-square test, and the Fisher exact test. Logistic regression predicted the risk of IAN injury. RESULTS: Although only 1.3% of the extractions caused temporary nerve damage, 25% of the lesions were permanent. All of the following significantly increased the risk of IAN damage (P < .05): age, the radiologic relationship between the apices and the mandibular canal, deflection of the root when approaching the mandibular canal, distal ostectomy, the distance of the apices of the third molar to the mandibular canal, ostectomy, crown sectioning, pain during root luxation, primary closure of the wound, prolonged operating time, bleeding, exposure of the nerve, and postoperative ecchymosis. The first 4 factors were included in a predictive logit model. CONCLUSIONS: Patient age, ostectomy of the bone distal to the third molar, the radiologic relationship between the roots of the third molar and the mandibular canal, and deflection of the mandibular canal increased the risk of IAN damage. Older patients were at a higher risk for suffering permanent injuries.

Adult↗
PubMed2000

Experimentally induced abutment strains in three types of single-molar implant restorations.

STATEMENT OF PROBLEM: The choice of single-molar implant design is difficult because of a lack of controlled, quantitative biomechanical analyses. PURPOSE: This study determined the effect of 3 single-molar implant designs on implant strains under a variety of homologous loading conditions. MATERIAL AND METHODS: On each implant abutment, 4 strain gauges were placed axially at 90 degrees to each other on the buccal, lingual, mesial, and distal surfaces. Effects of implant design, load location, direction, and magnitude were tested on axial and bending (buccolingual and mesiodistal) strains of 3 single-molar implant designs: (1) single, 3.75-mm (regular) diameter implant, (2) single, 5-mm (wide) diameter implant, and (3) two 3.75-mm diameter (double) implants connected through a single-molar crown. Results were analyzed with ANOVA. RESULTS: Variations in loading conditions induced 3-dimensionally complex abutment strains on the tested implant designs. Peak absolute strains in mesiodistal direction were 6493 microepsilon for design 1 and 3958 microepsilon on design 2, and 3160 microepsilon in buccolingual direction on design 3. For all loading conditions, the single 3.75-mm diameter implant consistently experienced the largest strains compared with wide-diameter and double implant designs. Changes in centric contact location affected implant abutment strains differently among the 3 designs. Angulated force direction resulted in larger bending strains. CONCLUSION: For single-molar implant designs, an increase in implant number and diameter may effectively reduce experimental implant abutment strains.

Analysis of Variance↗
PubMed2001

The relationship of handedness to asymmetry in the occlusal morphology of first permanent molars.

Handedness has been shown to be related to a number of systematic asymmetries in body dimensions, dermatoglyphic patterns and cerebral morphology. The aim here was to compare linear and angular tooth crown asymmetries of the permanent molars in healthy right-handed and left-handed subjects. The material comprised 27 children with recorded concordant left-side dominance of hand, eye and foot. The controls were an age- and sex-matched group with right side dominance. The material is based on the Collaborative Perinatal Project where detailed medical records and the dentitions, including accurate dental impressions, of over two thousand American children were examined in the USA in the sixties. Machine vision technique was used to obtain accurate three-dimensional information from the occlusal surfaces of the first permanent upper and lower molars. The directional asymmetry values of angular measurements of mandibular first molars showed evidence of asymmetry of opposite direction between the two examined groups. The results indicate that occlusal morphology of first permanent molars may be affected by handedness, and this tendency is most evident in the angular measurements of the mandibular molars. Fluctuating asymmetry did not differ significantly between the examined groups.

Child↗
PubMed1998

Timing of first fillings in the primary dentition and permanent first molars of asthmatic children.

The aim of this study was to analyze the timing of first fillings posteruptively in a cohort comprising 51 asthmatic children receiving inhaled corticosteroids and living in three communities in Ostrobothnia, Finland. They had all been born in the 1980s and had had asthma check-ups in the local asthma policlinic. A group of 102 healthy age- and sex-matched children served as controls. A longitudinal survival analysis of the timing of the first filling in the primary teeth and first permanent molars was conducted retrospectively using data from the annual dental health records. The timing of the first fillings in permanent first molars showed no statistically significant differences between asthmatic and healthy children, but the filling increments in the primary molars were consistently higher in the asthmatic group; the difference for the upper first primary molars was, for instance, statistically significant (risk ratio = 2.565; 95% confidence interval = 1.333-4.935). More extractions because of caries were also performed on primary molars in the asthmatic children. The findings support the hypothesis that factors related to the asthmatic condition might increase the risk of caries. A longer surveillance time would be needed to evaluate the effect of asthma on the permanent dentition.

Administration, Inhalation↗
PubMed1993

Emergence of the deciduous canines and molars in CLP children.

The emergence of the deciduous canines and molars was investigated as part of a longitudinal study into the emergence of the deciduous dentition in Dutch cleft lip and/or palate children (CLP) (Kramer et al., 1989). The study comprised a group of 71 CLP children and 74 normal children that served as a control. Mean emergence ages of the deciduous upper and lower canines and molars were studied. Emergence of the deciduous primary molar on the cleft side was delayed 2 months in the upper jaw and 1 month in the lower jaw in children with an unilateral cleft lip and palate. The deciduous primary molar on the non-cleft side was not delayed as compared with normal children. Local anatomical relationships could be a possible explanation for these findings. The deciduous canines and secondary molars in both jaws showed no significant differences in mean emergence ages as compared with the control group, nor between the different cleft types. No sex differences were found in any of the groups. A table is presented containing the mean emergence ages of all the teeth of the deciduous dentition for the various CLP-groups, divided in cleft and non-cleft side, and the control group.

Analysis of Variance↗
PubMed1998

Third molar impaction in extraction cases treated with the Begg technique.

The aim of this study was to investigate the differences between two groups of patients with either erupted or impacted mandibular third molars before and after orthodontic treatment. All patients were treated with Begg appliances following extraction of the four first premolars. The erupted group consisted of 14 subjects and the impacted group 13 subjects. Lateral cephalometric films, peri-apical radiographs, orthopantomographs and orthodontic casts of each subject were taken before and after treatment. Thirteen measurements were carried out on the lateral cephalometric radiographs. The results revealed slightly more vertical growth and a smaller mandibular arc angle in the erupted group at pre-treatment, and also a more upright lower third molar position and slightly greater distance between the distal point of the lower second molars and the centre of ramus (Xi) in the same group. In the course of treatment, mandibular third molars seemed less likely to erupt when the condyle grew vertically. The lesser resorption on the anterior border of the ramus might have played a part in this finding. In addition, a greater mesial inclination of the mandibular third molars might be an indication of the tendency for these teeth to be impacted in the present study.

Adolescent↗
PubMed2001

The effect of micro-etching on the retention of orthodontic molar bands: a clinical trial.

Failure of orthodontic bands occurs most frequently at the band-cement interface, when conventional glass ionomer cements are used. Modification of the band surface may improve clinical performance by increasing the mechanical interlock at this junction. The aim of this prospective study was to compare the retention of micro-etched and untreated first molar orthodontic bands in a randomized, half-mouth trial. Seventy-nine patients had 304 bands cemented as part of routine fixed appliance therapy. The effect of micro-etching, patient age and gender, operator, molar crossbite, treatment mechanics, and arch on band failure was investigated. Failure rates and survival times were compared for each variable assessed. Micro-etched molar bands showed a significant reduction in clinical failure rate over untreated molar bands and an increase in mean survival time (P < 0.001). Of the other variables examined, only the presence of a molar crossbite had any significant effect on band failure (P = 0.004).

Acid Etching, Dental↗
PubMed1997

Nickel-titanium coil springs and repelling magnets: a comparison of two different intra-oral molar distalization techniques.

The aim of this study was to compare two intra-oral molar distalization procedures, involving 15 cases with Class II molar relationships. Magnetic devices were applied to the upper right first molars in each case, while nickel-titanium coil springs were used against the upper left first molars, for a period of 3 months. Measurements were made from lateral cephalograms and from photocopies of models taken before and after the distalization procedure. Although upper molar distalization was achieved with ease in both techniques, nickel-titanium coil springs were found to be the more effective in terms of movement achieved.

Cephalometry↗