Second opinions in orthodontics can be of significant benefit to adult orthodontic patients (whether prospective or already under treatment) and to the parents of young orthodontic patients. They can amplify or clarify treatment recommendations, serve as cogent and ethical commentary on the quality of treatment, and inform parents and patients about the benefits, risks, and long-term implications of specific treatment options. The quality and value of a second opinion should be rooted in an expected high level of technical competence, critical thinking, and accepted orthodontic treatment standards. Above all, the second opinion should be firmly grounded in professional and ethical

Abstract

By 1892, Julius Wolff and others realized that mechanical loads can affect bone architecture in living beings, but the mechanisms responsible for this effect were unknown, and it had no known clinical applications. In 2003 we know how this effect occurs and some of its applications. Our load-bearing bones (LBBs) include tibias, femurs, humeri, vertebrae, radii, mandibles, maxillae, wrists, hips, etc (so LBBs are not limited to weight-bearing ones). The strength of such bones and their trabeculae would represent their most important physiologic feature but in the special sense of relative to the size of the typical peak voluntary loads on them. The biologic “machinery” that determines whole-bone strength forms a tissue-level negative feedback system called the mechanostat. Two thresholds make a bone's strains determine its strength by switching on and off the biologic mechanisms that increase or decrease its strength. Equally, two thermostats can determine a room's temperature by switching on and off the room's heating and cooling systems. General features show that the largest voluntary loads on LBBs determine most of their strength after birth. These loads come from muscle forces so muscle strength strongly influences the strength of our LBBs. This process affects, in part, the healing of fractures, bone grafts, osteotomies, and arthrodeses; the bone's ability to endure load-bearing joint and dental endoprostheses; why healthy bones are stronger than the minimum needed to keep voluntary loads from breaking them suddenly or from fatigue; some general functions and disorders of bone modeling and basic multicellular unit–based bone remodeling; some limitations of in vitro data and of pharmaceutical actions; and the fact that many bone-active humoral and local agents have permissive roles in a bone's adaptations and healing, instead of forcing them to occur.

Abstract

The aim of this study was to evaluate histological changes in the periodontal structures of beagle dogs after using high and low continuous forces during experimental tooth movement. An orthodontic appliance was placed on the second premolar and the first molar by exerting a continuous and constant reciprocal force of 25 cN on one side and 300 cN on the other side of the mandible. Tooth movement was recorded weekly. Dogs were sacrificed after one, four, 20, 40, and 80 days for histological evaluation. Hematoxylin and eosin (HE) staining was used for tissue survey, staining for alkaline phosphatase as a marker was used for active osteoblasts, and tartrate-resistant acid phosphatase staining was used for osteoclasts. After 24 hours, the remodeling process had already started at the pressure and tension side, and in some samples hyalinization was found. In contrast to earlier studies, hyalinization was found throughout the entire experimental period, both in molars and in premolars. In the periodontal ligament of some teeth, small patches of hyalinization were found at the pressure side, mostly located buccally or lingually of the mesiodistal plane, whereas others showed large areas of necrotic tissue. It is concluded that hyalinization limits tooth movement, but there is no relationship with the force level.

Abstract

The purpose of this study was to clarify the three-dimensional morphological characteristics of the dentition and palate in skeletal asymmetry in patients with skeletal Class III malocclusion using a newly defined palatal reference plane in a dental cast. Twenty patients (5 males and 15 females) who had skeletal Class III malocclusion with facial asymmetry were selected. Pretreatment posteroanterior cephalometric radiographs and maxillary dental casts were used. The lateral deviation of Me was measured as the distance from a line perpendicular to Lo-Lo′ that passed through CG. The angle between the Lo-Lo′ plane and the J-J′ plane was measured. Each maxillary dental cast was measured using a three-dimensional surface-scanning system, and the newly defined palatal reference plane was calculated. The right/left difference in the radius of curvature of the palate and right/left differences in the vertical and mesiodistal positions of the first molars were analyzed. Linear correlation and regression techniques were used. Our findings demonstrate that the lateral deviation of the mandible is closely related to the morphology of the alveolar process and to the vertical height of the dentition. In this study, the three-dimensional application of a new palatal reference plane is very useful in morphological research, and the results provide detailed information on the characteristics of facial asymmetry.

Effects of printing layer thickness and build orientation on the mechanical properties and color stability of 3D-printed clear aligners

Chengzan Wu,

Utkarsh Mangal,

Na Bai,

Hoon Kim,

Geelsu Hwang,

Jung-Yul Cha,

Kee-Joon Lee,

Jae-Sung Kwon, and

Sung-Hwan Choi

In Memoriam: Robert M. Rickettsa1920–2003

In Memoriam: Robert M. Ricketts ^a1920–2003