• The Journal of the Korean dental association
• /
• v.10 no.3
• /
• pp.149-153
• /
• 1972

The apical foramen is not always found on the very tip of the root. The apical foramen may make its exit on the mesial, distal, labial or lingual side of a root slightly short of the root apex rather than at the root apex itself. The author collected 43 upper first molars and 84 lower first molars as a samples. Apical foramens were carefully checked and examined these location on each tip. (table 1) 1. About 33% to 49% of upper cases were found on extreme tip of roots and the remaining cases were on the distal side or mesial side. 2. Except distal simple canal of lower molars, approximately 40% to 50% were located on the very tip of the root. The remaining cases were on distal or mesial surface. 3. On lower distal simple canal, about 51% of cases made its exit on distal side. The remaining cases located on the tip end or mesial side.

• Journal of Periodontal and Implant Science
• /
• v.23 no.1
• /
• pp.159-169
• /
• 1993

The thirty six mandibular second molars, which were extracted because of hopeless tooth due to advanced periodontal disease, were measured the length of mesial and distal root and the distance from cementoenamel junction to root separation. The molars were cross-sectioned every 1.5 milimeter from cementoenamel junction to root apex perpendicular to long axis and each section was photographed, projected and measured with a calibrated Digital Curvi-Meter(Com Curvi-8. Japan). The root surface area (RSA), percentage of the RSA and the linear variation of the RSA were calibrated for each 1. 5 mm section. The results were as follows. 1. The mean length of the roots was 12. 98mm for mesial root, 11.84 mm for distal root. The mesial root was longer than distal root.(p<0.01) 2. The mean distance from the cementoenamel junction to the point at which the root separate from the root trunk was 3.82mm for the buccal furcation and 4.75mm for lingual furcation. The buccal root separation was coronal than the lingual root separation.(p<0.01) 3. The total root surface area was $317.78mm^2$. 4. The mean surface area of the root trunk was $150.06mm^2$ and averaged 42.54% of the total root surface area. 5. The mean root surface area was $88.79\;mm^2$ for the mesial root, $78.93mm^2$ for distal root, The mesial root surface area was wider than the distal root surface area.(p<0.05) 6. In comparision, the mean root trunk surface area of the mandibular 2nd molar was wider than that of mandibular 1st molar(p<0.01), but each root of 2nd molar was smaller than that of 1st molar(p<0.01).

• Journal of Oral Medicine and Pain
• /
• v.17 no.2
• /
• pp.119-128
• /
• 1992

In order to evaluate the relationship of age with the developmental stage on mandibular second molars in female, the author examined the radiographs in standard films taken by intraoral paralleling technic and analysed the development of 620 roots of 310 females ranged from 10 to 18 years. The development was divided into 7 stages : Crown complete (Cr.C.), Root lengthed 1/4(R.1/4), Root length 1/2 (R.1/2), Rooth length 3/4 (R.3/4), Rooth length complete (R.C), Apex 1.2 closed (A. 1/2), Apical closure complete (A.C) The obtained results were as follows : 1. The formation of roots in fulllength of mandibular second molars was completed at 14.21-year-age in mesial root and at 14.96-year-age in distal root. 2. The formation of apical foramen of mandibular second molars was completed at 17.11-year-age in mesial root and at 17.53-year-age in distal root. 3. The mesial root of mandibular second molar was generally developed earlier than distal root (p<0.01) 4. Coefficients of correlation and regression equations between for age(Y) and the developmental stage of mandibular second molar(X) were "Y=1.53X+6.54, r=0.91 (p<0.01)" in mesial root and "Y=1.52X+7.11, r=0.92(p<0.01)" in distal root respectively.l root respectively.

• Journal of Periodontal and Implant Science
• /
• v.31 no.3
• /
• pp.573-579
• /
• 2001

The purpose of this study was to investigate the characteristiss of korean multi-rooted teeth extracted by periodontal disease. A total of 182 extracted multi-rooted teeth were examined. The distance from the cementoenamel junction(CEJ) to the root groove and from the CEJ to the root division was measured. The frequency of the root grooves were calculated. The results are as follows : 1. Distances from CEJ to the root groove were $1.53{\cdot}1.60mm$ for maxillary first premolars mesial${\cdot}$distal sides, $1.26{\cdot}1.38{\cdot}1.75mm$ for maxillary first molars buccal${\cdot}$mesial${\cdot}$distal sides, $1.38{\cdot}1.71{\cdot}1.41mm$ for maxillary second molars buccal${\cdot}$mesial${\cdot}$distal sides, $0.98{\cdot}0.99mm$ for mandibular first molars buccal${\cdot}$lingual sides and $1.28{\cdot}1.35mm$ for mandibular second molars buccal${\cdot}$lingual sides. 2. The frequency of the root grooves were $17.4{\cdot}30.4%$ for maxillary first premolars mesial${\cdot}$distal sides, $44.4{\cdot}84.1{\cdot}67.5%$ for maxillary first molars buccal${\cdot}$mesial${\cdot}$distal sides, $100{\cdot}90.3{\cdot}90.3%$ for maxillary second molars buccal${\cdot}$mesial${\cdot}$distal sides, $42.9{\cdot}77.8%$ for mandibular first molars buccal${\cdot}$lingual sides and 90.6% for mandibular second molars buccal${\cdot}$lingual sides. 3. Distances from CEJ to the root division were $6.8{\cdot}7.2mm$ for maxillary first premolars mesial${\cdot}$distal sides, $3.3{\cdot}4.38{\cdot}4.34mm$ for maxillary first molars buccal${\cdot}$mesial${\cdot}$distal sides, $3.67{\cdot}4.8{\cdot}4.07mm$ for maxillary second molars buccal${\cdot}$mesial${\cdot}$distal sides, $3.1{\cdot}3.89mm$ for mandibular first molars buccal${\cdot}$lingual sides and $3.2{\cdot}4.06mm$ for mandibular second molars buccal${\cdot}$lingual sides.

• Journal of Periodontal and Implant Science
• /
• v.34 no.3
• /
• pp.523-533
• /
• 2004

The purpose of this study was to evaluate the alveolar bone surface following root separation angle in the mandibular second molars. The fifty mandibular second molars(which were extracted) were selected, and the alveolar bone surface following root separation angle of the selected teeth were evaluated. The results were obtained as follows; 1. The root separation angle of fifty mandibular second molars were divided into three groups. The first $group(10-20^{\circ})$ was made up of ten teeth, the second $group(20-30^{\circ})$ was made up of fifteen teeth, and the third group(30-40$^{\circ}$) was made up of twenty-five teeth. 2. The mean root separation angle was $28.1^{\circ}$. The mean alveolar bone rate on the mesial surface of the mesial root was 44.27%, on the distal surface of the mesial root was 36.52%, on the mesial surface of the distal root was 33.45%, and on the distal surface of the distal root was 25.28%. 3. The mean alveolar bone rate on the distal surface of the mesial root, which composed the root separation area, was 32.95% in the first group, 36.06% in the second group, and 38.22% in the third group. The mean alveolar bone rate in the mesial surface of the distal root was 31.40% in the first group, 31.93% in the second group, and 35.18% in the third group. 4. The positive correlation was found between the root separation angle and the alveolar bone rate in the root separation area.(P<0.05) Although the mandibular second molar is a very important tooth in the oral cavity, its treatment and diagnosis is very difficult due to the variation of its root form. When periodontal disease involves the mandibular second molar, the result of this study assists in its treatment and diagnosis.

• Restorative Dentistry and Endodontics
• /
• v.7 no.1
• /
• pp.59-63
• /
• 1981

Ninety four human mandibular third molars were chosen to study the anatomy of the root canal. The experimental teeth were injected with china ink, decalcified, cleared and used in study, in vitro, to determine the number of root, the number of root canals, canals per root, frequency and location of transverse anastomoses, frequency and location of lateral canals and frequency of the apical deltas. The results were as follows: 1. Most of the teeth showed two canals, but 17.0% of the teeth were found to have one canal, 17.0% of them three canals, 3.2% of them four canals and l.1% of them five canals. 2. In so far as observing one canal per root, 17.0% of the teeth were found to have one canal in single-rooted tooth, 48.9% of them in mesial root and 58.5% of them in distal root. 3. In roots with two or three canals, the separated apical foramen appeared in 55.6% in single-rooted tooth, 64.3% in mesial side and 80.0% in distal side, and the common apical foramen appeared in 44.4% in single-rooted tooth, 35.7% in mesial side and 20.0% in distal side. 4. Of the two root canals in one root, 19.1% of the canals were found to have transverse anastomoses and were usually located in the apical third of the root. 5. 63.8% of 94 teeth were found to have lateral canals, and ramifications were mainly located in the apical third of the root.

• Restorative Dentistry and Endodontics
• /
• v.3 no.1
• /
• pp.7-11
• /
• 1977

One hundred and thirteen human mandibular first molars were injected with china ink, decalcified, cleared and used in study, in vitro, to determine the number of root, the number of root canals, canals per root, frequency and location of transverse anastomoses, frequency and location of lateral canals and frequency of the apical deltas. The results were as follows; 1. Most of the teeth showed three canals, but 21. 25% of the teeth were found to have two canals and 21. 25% of them four canals. 2. In so far as observing two canals per root, 77.0% of teeth were found to have two canals in mesial root and 25.7% of them in distal root. 3. In roots with two canals, the separated apical foramen appeared 59.8% in mesial side and 40.0% in distal side, and the common apical foramen 40.2% in mesial side and 60.0% in distal side. 4. Of the two root canals in one root, 37.3% of the canals were found to have transverse anastomoses and were usually located in the apical third of the root. 5. 25.7% of 113 teeth were found to have lateral canals, and ramifications were mainly located in the apical third of the root.

• Restorative Dentistry and Endodontics
• /
• v.5 no.1
• /
• pp.47-51
• /
• 1979

Fifty two human mandibular second molars were chosen to study the anatomy of the root canal. The experimental teeth were injected with china ink, decalcified, cleared and used in study, in vitro, to determine the number of root, the number of root canals, canals per root, frequency and location of transverse anastomoses, frequency and location of lateral canals and frequency of the apical deltas. The results were as follows; 1. Most of the teeth showed three canals, but 19.2% of the teeth were found to have two canals and 9.6% of them four canals. 2. In so far as observing two canals per root, 80.8% of the teeth were found to have two canals in mesial root and 9.6% of them in distal canal. 3. In roots with, two canals, the seperated apical foramen appeared in 59.5% in mesial side and 40.0% in distal side, and the common apical foramen appeared in 40.5% in mesial side and 60.0% in distal side. 4. Of the two root canals in one root, 36.2% of the canals were found to have transverse anastomoses and were usually located in the apical third of the root. 5. 23.1% of 52 teeth were found to have lateral canals, and ramifications were mainly located in the apical third of the root.

• The Journal of Korean Academy of Prosthodontics
• /
• v.36 no.2
• /
• pp.293-301
• /
• 1998

The purpose of this study was to investigate the effects of load on root that was applied to edentulous area in three simulated situation, in each case the guiding planes of abutment were right vertical, 95 degrees, or 100 degrees to residual ridge. The 2-dimensional finite element method was used and the finite element model was prepared as fellows. Right mandibular 1st and 2nd molar was lost and the 2nd premolar with distal rest was used as primary abutment which had three different degrees of guiding plane. Then 150N of compressive force was applied to central fossae of the 1st and 2nd molars and von Mises stress and displacement was measured. The results were as follows; 1. Irrespective of slopes of guiding planes, the stress was concentrated on mesial side of root apex and distal side of coronal portion of root, in particular on junction with distal alveolar bone. As slopes of guiding planes were increased. stress on root and compact bone surrounding abutment was increased but no considerable effect was seen on compact bone of residual ridge. 2. Distal side of coronal portion of root limited by periodontal ligament was displaced distally and mesial side of apical portion was mesially. With slope of guiding plane increasing, the pattern of displacement was similar with one another but the quantity was increased. 3. Both abutment & alveolar bone were displaced downward and root of abutment, especially distal side of coronal portion, was displaced severely. As the guiding plane was tiffed more mesially over $90^{\circ}$, the degree of displacement was also increased.

• Journal of Periodontal and Implant Science
• /
• v.24 no.1
• /
• pp.1-14
• /
• 1994

Dental calculus which is calcifing and/or calcified dental plaque is divided into supragingival calculus and subgingival calculus according to the position of deposit to gingival margin. Subgingival calculus has more important clinical significance in diagnosis and treatment of periodontal disease than supragingival calculus. In order to investigate the deposition pattern of subgingival calculus on each root surface of different tooth type, extracted 192 teeth due to excessive destruction of periodontal tissue were divided according to tooth type and the deposition pattern of subgingival calculus was classified into linear type, veneer type, scattered type, and aggregated type according to the configuration and the extent of deposit. The difference of percentage between each deposition pattern was statistically analyzed by Chi-Square test. Following results were obtained : l. In maxillary incisors, linear type and aggregated type were predominant deposition pattern of subgingival calculus on labial(45.5%, 36.4%) and palatal(36.4%, 36.4%) root surface, aggreated type(72.7%) was on mesial surface, and aggregated type(54.5%) and scattered type(36.4%) was on distal suface. 2. In mandibular incisors, scattered type, linear type and aggregated type were predominant deposition pattern of subgingival calculus on labial(33.3%, 30.6%, 27.8%) and lingual(36.1%, 30.6%, 25.0%) root surface, aggregated type(33.3%), scattered type(27.8% ), and veneer type(27.8%) were on mesial surface, and aggregated type(38.9%) and scattered type(33.3%) on distal surface. 3. In maxillary peremolars, the predominant deposition patterns of subgingival calculus were linear type(28.6%) on buccal root suface, scattered type(35.7%) and linear type(28.6%) on palatal surface, scattered type(39.3%) on mesial surface, aggregated type(46.4%) on distal surface, and aggregated type(53.6%) on furcation area. 4. In mandibular premolars, scattered type was predominant deposition pattern of subgingival calculus on buccal(39.3%) and lingual(50.0%) root surface, scattered type(32.1%) and aggregated type(32.1% ) were on mesial surface, and aggregated type(42.9%) was on distal surface. 5. In maxillary molars, aggregated type(40.0%) and scattered type(32.5%) were predominat deposition pattern of subgingival calculus on buccal root surface, aggregated type was on distal(40.0%) and furcation area(50.0%), but there was no predominat pattern on palatal and mesial root surfaces. 6. In mandibular molars, aggregated type(39.5%) and scattered type(28.9%) were predominant deposition patterns of subgingival calculus on buccal root surface, aggregated type(36.8%) was on lingual surface, linear type(39.5%) and aggregated type(34.2%) were on furcation area, but there was no predominant pattern on mesial and distal root surfaces.