pyri Co gh Not for Publicationt CLINICAL APPLICATION b y Q u i N n o t t r f e o ssence The Concept of the Interdental Gingival Midpoint Line in Cervical Line Management Takeshi Nozawa, DDS Private Practice, Ojiya, Niigata, Japan Shunzo Tsurumaki, CDT Sanjo, Niigata, Japan Satoshi Yamaguchi, DDS Private Practice in Orthodontics, Yotsukaido, Chiba, Japan Hiroaki Enomoto, DDS Clinical Professor, Oral Implant Center, Nippon Dental University, Niigata Hospital, Niigata, Japan Koichi Ito, DDS, MSD, PhD Professor and Chairman, Department of Periodontology, Nihon University School of Dentistry, Tokyo, Japan Correspondence to: Dr Takeshi Nozawa, Nozawa Dental Office, 9-7 Sakae-cho, Ojiya-shi, Niigata-Ken, 947-0011, Japan Tel: 81 258 82 0468; Fax: 81 258 82 0357; e-mail: [email protected] 46 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 4 • NUMBER 1 • SPRING 2009 pyri Co gh Not for Publicationt NOZAWA ET AL b y Q u i N n o t t r f e o ssence Abstract The first purpose of this study was to inves- ment through some clinical cases. In a tigate the relationship between the lowest thick-flat biotype case using a clinical cervical point and the interdental gingival crown lengthening procedure, the lowest midpoint (IGM) line in the maxillary anteri- cervical points were adjacent to the IGM or region. After marking the lowest cervical lines following long-term coronal gingival points and the mesial and distal interden- growth. In a short-term observation of a tal gingival midpoints on study models of thin-scalloped biotype case, untouched fa- 77 patients, the shortest distances from the cial gingiva increased following interdental IGM lines that connect both interdental gin- gingival augmentation. In a case of Miller gival midpoints to the lowest cervical points class 1 gingival recession, a coronally ad- were measured on silicone impressions. vanced flap combined with the roll tech- The findings showed that the average po- nique was performed based on the IGM sition of the lowest cervical points in the line concept. According to the results ob- central incisors coincides with the IGM line. tained from this study and these cases, it This position is located 0.24 mm palatally in seems that the IGM line could become a the lateral incisors, and in the canines diagnostic standard in cervical line man- 0.3 mm facially from the IGM line. The sec- agement in periodontal plastic surgery. ond purpose of the study was to verify the IGM line concept in cervical line manage- (Eur J Esthet Dent 2009;4:46–69). 47 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 4 • NUMBER 1 • SPRING 2009 pyri Co gh Not for Publicationt CLINICAL APPLICATION b y Q u i N n o t t r f e o ssence Introduction odontal biotypes.9 As well as pathologic fac- tors, periodontitis, brushing trauma, and The cervical line is constituted by the tooth malposition, are also considered to be boundary between the tooth and gingiva. In involved in causing gingival recession.10 a healthy periodontium, the marginal free The lowest cervical point is an important gingiva slopes coronally and ends in a factor in determining tooth form. The length round or thin edge.1,2 Changing of the cer- of gingival recession is usually measured vical line occurs with aging, following active by following the shortest distance from the and passive tooth eruption.3,4 In adults, the CEJ to the lowest cervical point. Various free gingival margin stops in the range of factors are considered to be causes of gin- 1.5 to 2.0 mm coronally from the cemento- gival recession. However, the concrete ele- enamel junction (CEJ).1,5 ments that affect the position of the lowest The apical shift of marginal free gingiva cervical point are unknown. from the CEJ is called gingival recession.6 Several surgical techniques have been Esthetic problems and dentin hypersensi- introduced for the improvement of gingival tivity sometimes occur in this area. Gingival recession since the 1950s. These include recession is caused by anatomic and laterally positioned and coronally advanced pathologic factors. The thickness of the pe- flaps, free gingival grafts, connective tissue riodontal tissue plays an important role in grafts, and guided tissue regeneration.10–12 gingival recession caused by the former. In Miller classified gingival recession into four line with previously published reports, the types in the light of predictability of root periodontal biotypes are usually classified coverage, and pointed out that a loss of in- into two types; thin-scalloped types and terdental papilla and buccal tooth malpo- thick-flat types.7, 8 It has been reported that sition affects success rate (Figs 1 to 8). In the possibility of gingival recession increas- orthodontic treatment, some studies have es in children and teenagers with thin peri- shown that lingual tooth movement caus- Fig 1 At first examination, the maxillary left lateral in- Fig 2 Following intrusion of the lateral incisor, loss of cisor is extruded compared with the central incisor. The interdental papilla can be observed between the cen- lowest cervical point of the lateral incisor is located at tral and lateral incisors. The lowest cervical point is lo- the center of the tooth. cated mesially. 48 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 4 • NUMBER 1 • SPRING 2009 pyri Co gh Not for Publicationt NOZAWA ET AL b y Q u i N n o t t r f e o ssence Fig 3 At first surgery, a connective tissue graft has Fig 4 The coronally advanced flap has been sutured been placed on the central and lateral incisors. for interdental papilla reconstruction. Fig 5 After orthodontic treatment, anterior teeth have Fig 6 One year after first surgery. Interdental gingival been stabilized using an A-splint. thickness has increased, and the interdental papilla has filled partially. The lowest cervical point has been displaced at the center of the tooth. Fig 7 At second surgery, a subepithelial connective Fig 8 Four years after second surgery. The interden- tissue graft using the tunneling technique has been tal papilla has almost filled following horizontal interden- placed in the interdental space. tal gingival augmentation. The lowest cervial point has been displaced more distally, indicating the change of interdental gingival thickness is related to the displace- ment of the lowest cervical point. 49 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 4 • NUMBER 1 • SPRING 2009 pyri Co gh Not for Publicationt CLINICAL APPLICATION b y Q u i N n o t t r f e o ssence es an increase in free gingival height.13,14 In line in cervical line management through recent years, two interesting articles have studying some clinical cases. reported improvements in the area of gin- gival recession using non-surgical treat- ments.15,16 However, the mechanisms in- Materials and methods volved have not yet been clarified. In esthetic implant dentistry, fixture posi- Study population tion is an important factor in obtaining suc- From 2006 to 2008, 77 patients (35 males cessful long-term results as well as hard and 42 females ranging from 10 to 57 and soft tissue augmentation.17–19 Several years of age, mean age 28.92±13.21 years authors have advocated the three-dimen- old) were selected from a private dental of- sional install position for the control of im- fice. All patients who participated were re- plant cervical lines.20–22 In facio-lingual quired to sign an informed consent state- placement, Saadoun et al21 stated that the ment at the beginning of the study. external implant collar surface should be 2 mm inside the buccal contour of the ad- Inclusion criteria jacent teeth. On the other hand, Enomoto22 The following entry criteria were used:23,24 stated that the collar of the implant should 1. symmetrical maxilla form from the mid- remain inside the virtual line that connects palatal suture cervical borders of adjacent teeth. Howev- 2. no periodontitis within 2mm probing depth er, there are very few reports on the horizon- in maxillary anterior teeth tal reference lines that are related to the po- 3. no gingival recession sition of the lowest cervical points in natural 4. no loss of interdental papilla teeth.23 The first purpose of this article is to 5. no excessive tooth rotation, investigate the relationship between the tooth extrusion, and incisal abrasion lowest cervical point and the interdental gin- 6. no caries, abrasion and restoration in the gival midpoint line in the maxillary anterior cervical area (Fig 9). region. The second purpose is to verify the concept of the interdental gingival midpoint Gingival biotypes were divided into two types using a CP11 periodontal probe. If the probe was visible during probing depth measurement, the gingival biotype was di- agnosed as a thin type. If the probe was not visible, the gingival biotype was diagnosed as a thick type.25 Measurement procedures Study models were made using alginate impressions. Firstly, the lowest cervical points in the maxillary anterior regions were determined bilaterally. The bilateral Fig 9 Normal maxillary anterior teeth devoid of destruc- points of mucogingival junction (MGJ), tive periodontitis were selected following the entry criteria. which are positioned apically from the low- 50 THE EUROPEAN JOURNAL OF ESTHETIC DENTISTRY VOLUME 4 • NUMBER 1 • SPRING 2009 pyri Co gh Not for Publicationt NOZAWA ET AL b y Q u i N n o t t r f e o ssence est cervical points were then determined for reference lines following Rose and App guidelines.26 Parallel lines were then drawn that passed through the lowest cervical points and lastly perpendicular lines were drawn from the top of the interdental papil- la to the reference lines.