Relationship between dental crowding and mandibular incisor proclination during orthodontic treatment without extraction of permanent mandibular teeth

Abstract

Objective: To examine changes in mandibular incisor proclination and protrusion resulting from alleviation of crowding. Materials and Methods: Records of 96 patients from a private practice treated without extractions or interproximal enamel reduction in the mandibular arch were included. Pre-and post-treatment cephalograms and models were examined to determine changes in incisor proclination, protrusion and crowding. Results: For every millimeter of crowding alleviation, increases in incisor proclination (DIMPA) and protrusion (DL1 to A-Pog) of 0.5u and 0.2 mm, respectively, were found, on average. High variability was calculated for both linear variables (that can be reduced by incorporating other variables by multilinear regression). Conclusions: For every millimeter of crowding alleviated, 0.5u of proclination and 0.2 mm of protrusion are expected. Our results indicate that proclination is mulifactorial and cannot be explained solely by the amount of crowding alleviated during orthodontic treatment. These results may be a useful guiding principle rather than a prognostic tool. (Angle Orthod. 2016;86:727-733.)

Separation of aligning and leveling stages to control mandibular incisor inclination: A randomized clinical trial

“…The results from this finding demonstrate two movements, first by round archwires and subsequently, by rectangular archwires. Other studies 5 - 8 , 27 , 29 reported the results from total treatment with durations of more than a year and included the finishing phase, which may affect the mandibular incisor position from wire bending, torqueing or intermaxillary elastics.…”

“…2 Results of very effective dental changes early in treatment after alignment and leveling showed that proclination of mandibular incisors was common, 3 especially in non-extraction orthodontically-treated cases. [4][5][6][7][8] Proclination of mandibular incisors may affect the esthetic outcome, surrounding periodontal tissues, 9 and treatment stability. 10 To correct crowded teeth, labial displacement of incisors is expected to gain spaces for tooth alignment.…”

“…10 To correct crowded teeth, labial displacement of incisors is expected to gain spaces for tooth alignment. [5][6][7][8]11 To reduce this flaring, rectangular archwires, which have the ability of torque control, should be placed at the beginning stage. 12 Unfortunately, the placing of rectangular NiTi archwires with 0.016 x 0.022-in is probably not possible since the dimension of 0.022-in of the archwire cannot be forced into the disordered bracket slots on crowded teeth.…”

Interproximal reduction in orthodontics: why, where, how much to remove?

“…16 The preservation of inter-canine width has been advocated to increase long-term stability in the mandible and, if IPR is used to gain space rather than expanding in the lower anterior region, the inter-canine width is more likely to be preserved. 19,20 A study examining cases 10 years post-retention investigated the long-term stability of treatment-induced changes of the maxillary and mandibular arch forms. 21 It was found that the arches tended to return to their pretreatment shape and that pretreatment arch form is the best guide for future arch form stability.…”

“…With an increasing number of patients using removable, aesthetic, orthodontic appliances, for whom extractions are often not advocated, the use of IPR as an alternative to gain space is becoming more popular. 5,20 The benefit of using IPR rather than extraction therapy to gain space is that it decreases overall treatment time, since the amount of stripping corresponds exactly with the amount of crowding. 27 Performing IPR when treating a case without any extractions also means that excessive advancement of the mandibular incisors can be avoided, 28 as well as overexpansion of the dental arches, while at the same time satisfactory alignment is still achieved.…”