2nd Premolars Research Articles

A New Hypo/Oligodontia Syndrome

Dental agenesis is either syndromic or non-syndromic. Here, we describe a familial case with Carvajal/Naxos syndrome associating woolly hair, palmoplantar keratoderma, and biventricular dilated cardiomyopathy. In addition to these signs, all three affected family members had hypo/oligodontia ranging from absence of the lower left second molar to 15 missing teeth, the typical pattern of oligodontia being absent 2nd premolars and absent 2nd and 3rd molars. Mutation screening in the desmoplakin gene (DSP) revealed a de novo missense mutation (c.1790 C>T, p.Ser597Leu) changing a serine residue conserved in all vertebrates. In addition, this variation was absent from 100 control DNA samples. There were no mutations in the plakoglobin gene. This familial case report and two other previous reports demonstrate that autosomal-dominant mutations in the DSP gene are associated with hypo/oligodontia in the setting of Carvajal/Naxos syndrome. This study suggests that dentists discovering oligo/hypodontia should screen for woolly hair and palmoplantar keratoderma because of the probable cardiac involvement with an inherent high risk of severe cardiomyopathy. In addition, this study reveals the role of desmosomes in the development of teeth and suggests that other genes encoding proteins of the desmosome could be involved in oligo/hypodontia.

Delayed dental maturity in dentitions with agenesis of mandibular second premolars

To evaluate dental maturity in the mandibular canine/premolar and molar innervation fields in children with agenesis of the 2nd mandibular premolar and to associate these findings with normal control material. Department of Orthodontics, Institute of Odontology, University of Copenhagen. Eighty-three panoramic radiographs (27 girls and 31 boys with agenesis of one mandibular 2nd premolar and 17 girls and eight boys with agenesis of both mandibular 2nd premolars) represented all mandibular second premolar agenesis cases from a material of 2847 radiographs. On each radiograph, dental maturity of all available mandibular premolars, canines and 2nd molars was evaluated and categorized in maturity stages according to Haavikko whose material served as control material. Descriptive statistics given by sample mean, standard deviation and range for each tooth stratified by gender and agenesis. Ninety-five percentage confidence limits and T-statistics were used. p-values <5% were considered significant. In unilateral agenesis, the canines are specifically delayed in both girls and boys, with a larger delay in girls (p=0.009). The second molar is not delayed in boys (p=0.98) but is in girls (p=0.04). The differences in delay for the canine compared to the second molar are significant for both girls and boys. The results show a considerable delay in tooth maturation within the canine/premolar innervation field predominantly in girls. The 2nd molar is delayed in girls but not in boys.

Marsupialization: A conservative approach for treating dentigerous cyst in children in the mixed dentition

Dentigerous cysts are usually encountered in the practice of pediatric dentistry. The treatment modalities range from marsupialization to enucleation of the lesion and are based on the involvement of the lesion with the adjacent structures. However, loss of a permanent tooth in the management of a dentigerous cyst can be devastating to a child who has already a congenitally missing tooth. The first case describes the technique of marsupialization in which we extracted the grossly carious deciduous 1st molar and created a window through the extracted socket to decompress the lesion. In this case the 2nd premolars were congenitally missing on both sides of the mandible for which we had not gone for enucleation of the dentigerous cyst along with the developing 1st premolar. The second case is a developmental type of a big dentigerous cyst where marsupialization was followed by enucleation of the cystic lining but without removal of the affected tooth. Both the teeth erupted in the oral cavity.

Mandibular Premolar Impaction

Literature specific to impacted premolars is not extensive despite the fact that mandibular 2nd premolars alone account for 2.4&#37; of dental impactions. The purpose of this paper is to describe the radical approach (extraction) of a transversally impacted 2nd premolar in the mandible through a lingual approach due to its peculiar position presuming it will contribute toward the literature regarding impacted mandible premolars.

Endodontic treatment of mandibular second premolar with three root canals using dental operating microscope

Mandibular premolars are one of the most difficult teeth to treat endodontically because of the variations in root canal anatomy(1). There are only a few endodontic publication citing an incidence of mandibular 2nd premolar with 3 root canals. Thorough knowledge of the basic root canal morphology as well as the possible anatomic variations is important for the successful treatment of such cases. This article describes the successful endodontic treatment of mandibular 2nd premolar with 3 root canals treated with the help of operating microscope in a patient with more than two canals also in the contralateral side second premolar. The success of endodontic treatment depends upon thorough debridement and complete obturation of the entire root canal system. For this the knowledge of roots and root canal morphology as well as the possible anatomic variations becomes very important (2,3). The canal morphology of mandibular 2nd premolar can be very complex and variable. Different studies have looked at the root canal morphology of mandibular premolars over years and reported a fairly high percentage of these teeth to have more than one canal.(4-6) Zillich and Dowson (7) have reported that an incidence of 0.4% of mandibular second premolars with three canals. Vertucci(8) does not report any case of mandibular second premolar with three or more canals at the apex. The incidence of three roots is extremely rare (0.1%). Such anatomic variations are quite possible and shouldn’t be thought of as exceptional. Dental operating microscope, with its magnification and illumination helps in the easy detection of hidden canals and allows a more detailed vision of the internal root canal system. With the use of microscope the success rate has definitely increased in the recent past. This article describes the successful endodontic treatment of mandibular 2nd premolar with three root canals with the help of dental operating microscope.

Transmigration of mandibular second premolar in a patient with cleft lip and palate: case report

Disturbances involving abnormalities in tooth eruption are named ectopia. Transmigration is the name assigned to ectopia in the presence of teeth in areas distant from the alveolar process. Initial angulation of the tooth bud of the second premolar and premature loss of permanent mandibular 1st molars can influence the distal migration of the second premolar. Some studies have observed that ectopic teeth can be found in a variety of places around the oral cavity and also in other areas of the human body. There are records of teeth in the maxillary sinus, mandibular condyle, coronoid process, mandibular angle, orbit, palate, mentum and also the skin. The prevalence of tooth abnormalities is higher in children with cleft lip and palate compared to children without clefts. This paper presents a case report of migration of the mandibular left second premolar in a patient attending the Hospital for Rehabilitation of Craniofacial Anomalies of the University of São Paulo (HRAC/USP), Brazil. Migration of the mandibular left 2nd premolar was confirmed by 8 panoramic and 1 periapical radiographs obtained during patient's treatment between 1978 and 2002, which were available in the files of the Department of Dental Radiology of HRAC/USP. It can be assumed that distal migration of the mandibular left 2nd premolar is not associated with presence of cleft lip and palate; observation of these two events in a same patient is rare, since no similar reported cases were found in the literature.

Histometric Analysis of Immediate Implantation and Immediate Loading of CMP and RBM Implants after Tooth Extraction in Dogs

This study analyzed immediate implantation and immediate loading of chemical mechanical polished (CMP) and resorbable blast media (RBM) SSIII OSSTEM dental implants histometrically. The 1st, 2nd, 3rd, and 4th mandibular premolars were extracted from five adult dogs. Immediate implantation was performed in the fresh extraction sockets. Each dog received two types of implant: CMP and RBM. The first premolar was submerged, whereas the second, third, and fourth were not submerged. The implants were splinted using acrylic resin and subjected to immediate loading. After 4 months, X-rays were taken and analyzed. The animals were euthanized and processed histologically to obtain non-decalcified sections. Longitudinal ground sections of each implant were made, and histometry was analyzed under light microscopy. No significant difference was found between the control and experimental groups based on immediate loading (p &gt; 0.05) and implant surface (p &gt; 0.05). The implant survival rate and implant-to-bone contact rate after immediate loading were similar to those of submerged implants. The CMP and RBM dental implants did not differ in terms of implant survival rate and implant-to-bone contact rate.

Developmental stages of permanent canines, premolars, and 2nd molars in 244 Danish children

Objective. The purpose of this study was to establish reference values for maturity of permanent canines, premolars, and permanent 2nd molars in Danish children, and to focus on differences between the right and left sides, males and females, and the maxilla and mandible. Material and Methods. Panoramic radiographs from 106 males (8–14 years) and 137 females (7 years 2 months to 13 years 8 months) were analyzed, along with the maturity of the canines, premolars, and 2nd molars in each radiograph. Each tooth was categorized according to Haavikko's crown and root morphology. Inter-observer reliability was performed. For statistical analysis, Bowker's test was used for symmetry evaluation and comparison of maturity in the maxilla and mandible. The association between stage and age was presented by cumulative distributions. The Wilcoxon rank sum test was used for evaluating differences between genders. Results. Differences in maturity between the left and right sides were non-significant. A significant difference in dental maturity was observed between males and females, except for the maxillary 2nd premolar. Females matured earlier than males. The mandibular canines matured significantly earlier than the maxillary canines in females. No significant differences between the jaws were observed in the maturation of the premolars and 2nd molars. Conclusion. These reference values for dental maturity can be useful in orthodontic treatment planning and as a reference for odontological forensic age determination.

Mandibular radiomorphometric measurements as indicators of possible osteoporosis in postmenopausal women

ObjectiveThe use of mandibular anatomic indicators on panoramic radiographs, i.e. the number of lost teeth, mandibular cortical width at the mental region (MCW), panoramic mandibular index (PMI), alveolar crest resorption degree (M/M ratio) and morphologic classification of the mandibular inferior cortex (MIC grade) can be useful in the evaluation of bone resorption in different age groups of women to determine the presence of osteoporosis. The purpose of this study was to assess the validity of mandibular radiomorphometric measurements and to determine the frequency of tooth loss in postmenopausal women. Subjects and methodsAn assessment of the number of lost teeth, MCW, PMI, M/M ratio and MIC grade was performed on dental panoramic radiographs in a group of 133 postmenopausal women 38–80 years-of-age.BMD at the lumbar spine was measured by dual energy X-ray absorptiometry. BMD values were categorized as normal (T-score greater than 1.0), and as indicative of osteopenia (T-score −1.0 to −2.5) or osteoporosis (T-score less than −2.5) according to the World Health Organization classification. ResultsIn our study when the T-score at the lumbar spine is decreased, the age of menopause is increased, and the MCW is decreased to a point of statistical significance. A decrease in MCW by 1mm increases the likelihood of osteopenia or osteoporosis to 43%, having taken into consideration the effect of the years elapsed since menopause. It was also shown that age, years since menopause, MCW value, and the number of teeth lost have a statistically important effect on the incidence of moderate or severe cortical erosion. Moreover, when the MCI is C2 or C3 (mild or severe erosions) the age is increased, the years since menopause are increased and the MCW is decreased to a point of statistical significance. As far as tooth loss is concerned, an increase by 1unit in the number of teeth lost, increase the likelihood of moderate or severe erosion to 6%, having taken into account the years elapsed since menopause. Our study also demonstrated that postmenopausal women tend to lose their teeth at an age older than 50 years. They usually lose the 1st and 2nd mandibular molars and the 1st and 2nd maxillary premolars. Loss of front teeth and canines occurs at an age older than 60 years (except for the lateral maxillary incisors). At a younger age they tend to lose the 2nd maxillary premolars more frequently than their mandibular counterparts. ConclusionsIn conclusion, panoramic radiographs constitute an integral part of almost every routine dental evaluation and can be useful for the early diagnosis of osteoporosis in postmenopausal women. Dentists have sufficient clinical and radiographic information that enables them to play a significant role in patient screening for osteoporosis.

Forces applied by anterior and posterior teeth and roles of periodontal afferents during hold-and-split tasks in human subjects

Hold-and-split tasks were performed by 20 subjects (12 females and 8 males) using the right central incisors, canines, 2nd premolars, and 1st molars, respectively. Half a peanut was positioned on a transducer-equipped plate and the subject was instructed to hold the plate with the peanut between two antagonistic teeth, and not using more force than necessary. After ca. 3 s the subject was instructed to split the peanut in a natural manner. Each session consisted of a series of three in which the subject performed the hold-and-split task five times for each tooth. Thus, in total, data were obtained from 60 trials for each subject. The magnitude of the forces and the force rates used to split the peanut increased distally along the dental arch. However, the duration of the split phase was similar for the various teeth examined. During anesthesia of the periodontal ligament (four subjects), no significant changes were seen in the split phase. The forces used to hold the peanut between the teeth also increased distally along the dental arch: 0.60 N for the incisor, 0.77 N for the canine, 1.15 N for the 2nd premolar, and 1.74 N for the 1st molar. The difference in hold forces for the various teeth can be explained by the different sensitivity characteristics of the periodontal afferents innervating anterior and posterior teeth. During periodontal anesthesia, the magnitude and variability of the hold forces increased for all types of teeth, thus supporting the suggestion that periodontal afferent information is used in the regulation of the level of forces used to hold and manipulate morsels between the teeth.

Stress analysis of implant‐supported partial prostheses in anisotropic mandibular bone: in‐line versus offset placements of implants

Three-dimensional, anisotropic finite element models were executed to investigate the biomechanical effects of in-line and offset placements of implants on implant-supported partial prostheses. Three implant placements of finite element models were created: in-line, buccal offset and lingual offset placements. The mesh models of a cadaver mandibular segment and a three-united crown containing the 2nd premolar, the 1st molar and the 2nd molar were constructed by computer tomography images. The material properties of mandible were applied as transversely isotropic and linearly elastic. Two loading modes (100N), vertical and oblique, were evaluated in all models. Insignificant difference was observed in implant stresses between the in-line and offset placements under the vertical loading mode. Under the oblique loading, however, the offset placement decreased the implant stress by a maximum of 17%. The maximum stress at cortical bone and trabecular bone around each implant did not show conspicuous difference between the in-line and offset placements. This study demonstrated the mechanisms of how stresses were distributed between the in-line and offset placements. Even though the offset placements showed the benefit of decreasing implant stresses, justified from the bone stress the offset placements provided no advantage for the stress decreasing over the in-line placement.

Dental abnormalities in permanent dentition in children with submucous cleft palate

Seventy‐three children with submucous cleft palate (38 girls and 35 boys), mean age 8.2 years (range 7.7–9.5), were studied retrospectively from orthopantomograms. Dental abnormalities in permanent dentition were found in 26 patients (36%). Missing teeth, mainly lower 2nd premolars, upper lateral incisors, and upper 2nd premolars, were found in 12 patients (16%). Most of the patients had 1 or 2 missing teeth, 2 had 3 missing teeth. In 5 patients hypodontia was associated with another dental abnormality. Other dental abnormalities included peg‐shaped lateral incisors in 7 patients (10%), ectopic eruption of upper 1st molars in 6 patients (8%), transposition of upper canines and 1st premolars in 3 patients (4%), supernumerary teeth in 2 patients (3%), and palatally displaced upper canines in 1 patient (1%). As children with submucous cleft palate have a tendency towards increased frequency of missing teeth and other dental abnormalities, the need for thorough clinical and radiological dental examination is emphasized.

Prevalência de raízes supranumerárias em pré-molares inferiores

&lt;span class="texto"&gt;As raízes supranumerárias são uma alteração de desenvolvimento que pode envolver qualquer dente, e o conhecimento de sua ocorrência é particularmente importante para a realização de tratamento cirúrgico ou endodôntico da unidade afetada. Diante dessa realidade, procuramos determinar a prevalência de raízes supranumerárias em pré-molares inferiores. O estudo foi realizado com 200 exames radiográficos periapicais de toda a boca, perfazendo um total de 800 dentes. Optamos por essa metodologia devido à possibilidade de analisar radiografias de caninos, pré-molares e molares inferiores, tendo-se uma variação na angulação horizontal que permitiu a identificação de raízes sobrepostas na incidência ortorradial. As radiografias foram submetidas à avaliação de um radiologista experimentado e os dados levantados foram submetidos a tratamento estatístico através de gráfico de setores. Os resultados encontrados demonstram que 14% (112) dos dentes avaliados apresentaram raízes supranumerárias, nos quais 56% ocorreram no sexo masculino e 44% no feminino. Quanto ao nível de emergência, 61% foram no terço médio, 38% no apical e 1% no terço cervical da raiz. O dente mais envolvido foi o primeiro pré-molar, num total de 70% dos casos, contra 30% de segundos pré-molares. Em relação ao tipo de ocorrência, 67% foram unilaterais e 33% bilaterais, sendo que, desses últimos, 82% ocorreram em primeiros pré-molares e 18% nos segundos pré-molares inferiores.&lt;/span&gt;

Caries‐preventive effect of fissure sealants: a systematic review

The objectives of this study were to evaluate systematically the evidence of the caries‐preventive effect of fissure sealing of occlusal tooth surfaces and to examine factors potentially modifying the effect. The search strategies included electronic databases, reference lists of articles, and selected textbooks. Inclusion criteria were randomized or quasi‐randomized clinical trials or controlled clinical trials comparing fissure sealing with no treatment or another preventive treatment in children up to 14 years of age at the start; the outcome measure was caries increment; the diagnostic criteria had been described; and the follow‐up time was at least 2 years. Inclusion decisions were taken and grading of the studies was done independently by two of the authors. The main measure of effect was relative risk reduction. Thirteen studies using resin‐based or glass ionomer sealant materials were included in the final analysis. The results showed that most studies were performed during the 1970s and a single application had been utilized. The relative caries risk reduction pooled estimate of resin‐based sealants on permanent 1st molars was 33% (relative risk=0.67; CI=0.55-0.83). The effect depended on retention of the sealant. In conclusion, the review suggests limited evidence that fissure sealing of 1st permanent molars with resin‐based materials has a caries‐preventive effect. The evidence is incomplete for permanent 2nd molars, premolars and primary molars and for glass ionomer cements. Overall, there remains a need for further trials of high quality, particularly in child populations with a low and a high caries risk, respectively.

The effect of a fibrin glue on the integration of Bio-Oss with bone tissue. A experimental study in labrador dogs.

Bio-Oss is a deproteinized bovine mineral used in bone augmentation procedures. The particles are often mixed with a protein product (Tisseel) to form a mouldable graft material. The aim of the present experiment was to study the healing of self-contained bone defects after the placement of Bio-Oss particles alone or mixed with Tisseel in cylindrical defects in the edentulous mandibular ridge of dogs. In 4 labrador dogs, the 2nd, 3rd and 4th mandibular premolars were extracted bilaterally. 3 months later, 3 cylindrical bone defects, 4 mm in diameter and 8 mm in depth, were produced in the right side of the mandible. Following a crestal incision, full thickness flaps were raised and the bone defects were prepared with a trephine drill. The defects were filled with Bio-Oss (Geistlich Biomaterials, Wolhuser, Switzerland) particles alone or mixed with Tisseel (Immuno AG, Vienna, Austria), or left "untreated". A collagen membrane (Bio-Gide, Geistlich Biomaterials, Wolhuser, Switzerland) was placed to cover all defects and the flaps were sutured. 2 months later, the defect preparation and grafting procedures were repeated in the left side of the mandible. After another month, the animals were sacrificed and biopsies obtained from the defect sites. Bio-Oss-treated defects revealed a higher percentage of contact between graft particles and bone tissue than defects treated with Bio-Oss+ Tisseel (15% and 30% at 1 and 3 months versus 0.4% and 8%, respectively). Further, the volume of connective tissue in the Bio-Oss treated defects decreased from the 1 to the 3 month interval (from 44% to 30%). This soft tissue was replaced with newly formed bone. In the Bio-Oss+ Tisseel treated defects, however, the proportion of connective tissue remained unchanged between 1 and 3 months. The adjunct of Tisseel may jeopardize the integration of Bio-Oss particles with bone tissue.

Hypodontia of permanent teeth in a Kenyan population.

To assess the occurrence of hypodontia (except 3rd molars) in a population of orthodontic patients. A retrospective case study. Private orthodontic practice in Nairobi Six hundred and fifteen orthodontic patients aged eight to fifteen years. Hypodontia occurred in 39 children (6.3%). The missing teeth were observed in 24 males (7.2%) and 15 females (5.3%). Of the children with hypodontia, about 80% lacked one or two teeth, 54% had hypodontia involving anterior teeth, 18% lacked single posterior teeth and 8% had two or more teeth missing in the same quadrant. The highest recorded number of missing teeth in any one individual was seven. The most frequently missing teeth were mandibular 2nd premolars (30%), maxillary 2nd premolars (24%) and maxillary lateral incisors (22%) in that order. Our data for hypodontia were within the wide range reported in the literature. The finding of patients with hypodontia involving the anterior teeth and others missing more than two teeth in the same quadrant was an indication of a great need for orthodontic treatment. The present findings reiterate the neeed for a thorough radiographic evaluation of patients prior to removal of permanent teeth for orthodontic reasons.

Orthodontic movement in bone defects augmented with Bio‐Oss®

AbstractObjective: To study if it was possible to move, by orthodontic means, a tooth into an area of the jaw that had been augmented with Bio‐Oss®.Material and Methods: 5 beagle dogs were used. The 1st, 2nd, and 4th mandibular premolars on each side were removed. The defect at the left 4th premolar site was filled with a biomaterial (Bio‐Oss®) while the corresponding defect in the right side was left for spontaneous healing. 3 months later, an orthodontic device was inserted in each side of the mandible. The device was designed to allow distal, bodily movement of the 3rd premolars. When the experimental teeth had been moved into the extraction sites of the 4th premolars, the animals were sacrificed and biopsies of the premolar‐molar regions of the mandible sampled. The tissues were prepared for histological analysis using standard procedures. In the sections, 3 zones were identified: zone A=the bone tissue within the distal portion of the previous extraction site (4th premolar), zone B=the pressure side of the 3rd premolar, zone C=the tension side of the 3rd premolar. The area occupied by mineralized bone, Bio‐Oss® particles and bone marrow was determined by a point counting procedure. The width of the periodontal ligament as well as the percentage of the root surface (in zone B) that exhibited resorption was determined.Results: The findings demonstrated that it was possible to move a tooth into an area of an alveolar ridge that 3 months previously had been augmented with a biomaterial. It was also demonstrated that 12 months after grafting, Bio‐Oss® particles remained as inactive filler material in the not utilized part of zone A. The biomaterial was not present in zone C but present in small amounts in zone B.Conclusion: During the orthodontic tooth movement the graft material (Bio‐Oss®) was degraded and eliminated from the part of the alveolar ridge that was utilized for the experiment. In the non‐utilized part of the ridge the biomaterial, however, remained as a seemingly inactive filler material.

Orthodontic movement in bone defects augmented with Bio-Oss. An experimental study in dogs.

To study if it was possible to move, by orthodontic means, a tooth into an area of the jaw that had been augmented with Bio-Oss. 5 beagle dogs were used. The 1st, 2nd, and 4th mandibular premolars on each side were removed. The defect at the left 4th premolar site was filled with a biomaterial (Bio-Oss) while the corresponding defect in the right side was left for spontaneous healing. 3 months later, an orthodontic device was inserted in each side of the mandible. The device was designed to allow distal, bodily movement of the 3rd premolars. When the experimental teeth had been moved into the extraction sites of the 4th premolars, the animals were sacrificed and biopsies of the premolar-molar regions of the mandible sampled. The tissues were prepared for histological analysis using standard procedures. In the sections, 3 zones were identified: zone A=the bone tissue within the distal portion of the previous extraction site (4th premolar), zone B=the pressure side of the 3rd premolar, zone C=the tension side of the 3rd premolar. The area occupied by mineralized bone, Bio-Oss particles and bone marrow was determined by a point counting procedure. The width of the periodontal ligament as well as the percentage of the root surface (in zone B) that exhibited resorption was determined. The findings demonstrated that it was possible to move a tooth into an area of an alveolar ridge that 3 months previously had been augmented with a biomaterial. It was also demonstrated that 12 months after grafting, Bio-Oss particles remained as inactive filler material in the not utilized part of zone A. The biomaterial was not present in zone C but present in small amounts in zone B. During the orthodontic tooth movement the graft material (Bio-Oss) was degraded and eliminated from the part of the alveolar ridge that was utilized for the experiment. In the non-utilized part of the ridge the biomaterial, however, remained as a seemingly inactive filler material.

Thickness of masticatory mucosa.

The aim of the present study was to assess thickness of all parts of the masticatory mucosa by using an ultrasonic measuring device. A total of 40 periodontally healthy subjects, 19 to 30 years old, took part. Thickness of masticatory mucosa was measured at a maximum of 149 sites in each proband. Female volunteers had significantly thinner mean masticatory mucosa than males (p<0.01). Mean thickness of facial gingiva ranged between 0.7 mm at canines in the maxilla and central incisors in the mandible and 2.3 mm at 3rd molars in the mandible. In the mandible, thickness of lingual gingiva ranged between 0.9 mm at lateral incisors and 2.3 mm at 3rd molars. Interdental gingiva ranged between 1.0 mm 2.1 mm. With 3 mm or more, on average, palatal masticatory mucosa was thickest in the 3rd molar region and at 2nd premolars at more central locations. 2 regions with comparatively thin palatal mucosa of about 2 mm were identified, namely (i) at central and lateral incisors and (ii) at the prominence of the palatal roots of 1st and 2nd molars. The thickest tissue with more than 4 mm, on average, was observed in the tuberosity and retromolar regions. Considerable intra- as well as interindividual variation of thickness of masticatory mucosa could be observed. According to differences in thickness of facial and interdental gingiva, it appears that lining is also an important function of the gingiva in reducing and smoothing the pronounced convexities of the dentoalveolar, i.e., skeletal, complex.

The Usefulness of Panoramic Radiography using a Lead Ruler for Dental Implant Planning

Purpose: If damage to the neurovascular bundle of the mandibular canal during dental implant surgery of the mandible is to be prevented, accurate measurement of the distance between the alveolar crest and the mandibular canal, as seen on panoramic radiographs, is important. The purpose of this study was to compare the accuracy of panoramic radiography using a lead ruler with that of computed tomography for the measurement of the distance between the alveolar crest and superior border of the mandibular canal and to evaluate the usefulness of panoramic radiography using a lead ruler. Materials and Methods: For control study, panoramic radiography of the dry mandible was undertaken using a lead ruler, and computed tomography was added. The distances between the alveolar crest and the superior border of the mandibular canal and between the alveolar crest and the lowest border of the body of the mandible were measured at the level of the 2nd premolar to the 3rd molar. These measurements were compared with actual measurements of the dry mandible in the same areas. The cases of 87 patients[49 men, 38 women; age range, 20-84 (mean, 42) years] who had undergone panoramic radiography using a lead ruler were reviewed. They were catergorized according to sex, the presence of teeth, and whether under or over 50 years of age. All measurements were compared and analyzed using the Student t-test. Results: Measured values obtained from a panoramic radiograph using a lead ruler(magnification:100.32%5.92) and from a computed tomograph(magnification:100.22%5.55) deviated less from actual measurements on the dry mandible (p 0.05). The distance from the 2nd premolar to the 3rd molar was greater in male adults (19.62 mm 3.95) than in female (17.54 mm 4.04) (p 0.05), except the 3rd molar. In addition, the distance was greater in dentulous patients(18.81 mm 3.33) than in edentulous (16.23 mm 1.75)(p 0.05), except the 3rd molar. There was, howerer, no significant difference between patients under and over 50 years of age (p 0.05), except 2nd pre molar and 1st molar in the female. Conclusion: Panoramic radiography using a lead ruler is a simple and accurate modality for the presurgical planning of dental implant surgery. It is suggested that the successful long-term rate of dental implantation may be higher in dentulous male than in edentulous female molars.